© 2024, Academia Brasileira de Ciencias. All rights reserved.The transmission gearbox of military helicopters, such as the H225M, experiences intense dynamic loads, leading to the detachment of ferromagnetic particles, often due to wear or fatigue. This poses safety risks, as excessive particle detachment demands stringent maintenance. To address this, the study applies machine learning algorithms to predict particle detachment using data from the Flight Data Recorder and Health and Usage Monitoring System. The approach aims to mitigate operational challenges faced by the Brazilian H225M fleet while considering aviation safety criteria and the pre-processing needs for an effective machine learning application.

© CSP - Cambridge, UK; I&S - Florida, USA, 2024In this work, the influence of magneto-rheological fluid embedded on journal bearings in the dynamic behavior of rotors is considered. The modified Reynolds equations for Bingham viscoplastic materials are used for calculation of the nonlinear hydrodynamic forces. Flexible rotors are modeled by the finite element method. The static weight of the rotor, unbalance and bearing hydrodynamic forces are included in the equations of motion. Non-linear hydrodynamic forces calculation depends on the relative positions of the journal bearings. The dynamic system response is computed by the Newmark method modified to obtain the calculation of the differential displacements and velocities for each time step. By incorporating the Newton-Raphson method the necessary corrections are included in the equations of motion. Time and frequency responses are presented for two of the case studies. The sudden elevation in oscillation magnitudes due to the oil whip phenomenon is not observed in the run-up test after the application of electromagnetic induction on the MR fluid. Furthermore, the controlled variation in the viscosity of the MR fluid causes significant changes in the bearing movements, as demonstrated by the orbit graphs.

© Published under licence by IOP Publishing Ltd.This research performs a nonlinear analysis of a typical section airfoil limited to two degrees of freedom emphasizing the evaluation of the effects of a quartic structural stiffness on dynamic responses. Analytical studies are presented based on a simulated model. First, the influence of the quartic term of nonlinear structural stiffness in spring moment is evaluated. Then, phase portraits are presented as a function of freestream velocity, and a time domain decomposition of time histories is performed to identify the limit cycle frequency. Additionally, it maps the region of limit cycle oscillations (LCOs). Furthermore, the aim of this work is to characterize the nonlinear aeroelastic response.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.The vibration energy collectors based on piezoelectric resonators are promising elements for energizing remotely located systems. However, differences between the resonant frequency of these traditional harvesters and the vibration frequency can drastically decrease the collected energy and make them ineffective. Appropriate mathematical models, different analyses, and optimization techniques to tune the resonant frequency of piezoelectric collectors have been researched. In this study, the model of an inverted vertical cantilever beam with a piezoelectric patch and a tip mass is used for energy harvesting. The beam is subjected to base excitations that can induce large lateral displacements of the tip, and consequently large deformation for the piezoelectric patch. Applying the homotopy analysis method (HAM) to the coupled electromechanical governing equations of motion, novel analytical solutions of the transverse displacement of the cantilever beam, its amplitude and phase as well as the output voltage obtained from the piezoelectric patch are derived. The analytical solutions are derived for the transversal displacements of the beam, even if it presents a varying cross-sectional area. The analytical solution considers the nonlinear behavior characteristics emphasizing the capabilities of a first-order approximation of HAM to present highly accurate closed-form solutions. The accuracy of this approximation of HAM is confirmed by comparison to numerical integration methods.

© 2024 Elsevier Inc.The present manuscript delineates the derivation of strong solutions for the linear elasticity problem in a two dimensional rectangular beam. The materials under consideration can exhibit either isotropic or orthotropic properties. Additionally, the analysis is not restricted to slender beams because the ratio between the length and the height of the beam can be arbitrary. The boundary conditions fall into the Dirichlet category, implying that both horizontal and vertical displacements are specified on all four surfaces. The sole requirement is that these surface displacements are continuous functions, although they may not necessarily be smooth. Since the displacements at the surfaces can be arbitrary, there is no need to consider approximations, such as those concerning local (small) boundaries in slender beams. Nonetheless, it is demonstrated that an equivalent principle to the Saint-Venant principle exists for pure displacement boundary conditions. The partial differential equations are solved through the separation of variables method, leading to the identification of two solution types, encompassing both cosine and sine Fourier series. Particular emphasis is placed on evaluating the convergence of these solutions. For two distinct and general examples, it is confirmed that the solutions indeed exist.

© 2024 The Authors. Published by Elsevier B.V.Additive Manufacturing (AM) is vital for industrial innovation, offering high potential for groundbreaking solutions. However, its successful implementation still depends on overcoming several challenges. Particularly, the assessment of surface integrity in AM-generated components, and its degradation when subjected to contact stresses presents an ongoing endeavor. Within this context, the current work delves into the study of the surface integrity of 20MnCr5 case-hardened samples manufactured through laser powder bed fusion (L-PBF), as well as delves into the investigation of surface failure progression when the samples are subjected to cyclic contact stresses. This study encompasses the analysis of residual stresses, hardness, and roughness of specimens manufactured through both additive and conventional production routes. The study's findings show that it is feasible to attain analogous surface quality when proper finishing is applied to L-PBF samples. Although, despite the comparable surface quality, the contact fatigue performance was significative lower on the AM sample when compared to the conventionally manufactured. Additionally, additive manufacturing brings up new challenges to performance by presenting a heterogeneous stress distribution and sub-superficial porosity. In conclusion, to attain a desirable surface integrity for additive manufactured parts, further research should not only focus on improving the process parametrization but should also developing finishing routes especially oriented to additive manufacturing, considering therefore how the interaction between the manufacturing processes will evolve into a desirable surface integrity state.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work proposes an assessment of the delta wing sweep variation of a Generic Future Fighter in the conceptual design phase. Combat aircraft have critical control and therefore the stability analysis of these configurations is compared. Little variation in stability was observed between the 5 different configurations. This indicates that other requirements may become more relevant when designing a fighter aircraft, such as stealth and performance. Thus, this work aims to evaluate the impact of wing sweep on the longitudinal stability of fighter aircraft, considering five different sweep angles: 45°, 47°, 50°, 55°, and 60°. To conduct this analysis, a numerical evaluation, using the Vortex Lattice Method (VLM), wind tunnel results and parameter identification data from past work will be used to obtain the aerodynamic data for each configuration. The aerodynamic data will then be used in a time-domain flight simulation model to analyze the longitudinal stability of the aircraft.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The upward variation in altitude implies a decrease in air density. This phenomenon induces modifications in the aerodynamic forces and moments exerted on an aircraft, especially in combat aircraft. Such alterations have profound implications on the stability and controllability of the aircraft, thereby necessitating the implementation of distinct control strategies contingent upon the altitude. Conventional control systems, which are typically calibrated for a pre-defined set of environmental conditions, may not exhibit optimal performance throughout the entire range of operational altitudes encompassed within the flight envelope. This research work analyzes the Generic Future Fighter (GFF) subscale model and has as its central proposition the use of Linear Matrix Inequalities (LMIs) in the design of a Stability Enhancement System (SAS) for the aircraft, the in order to guarantee stability and maintain performance at different operating altitudes. The results obtained from the simulation showed that the open-loop response presents significant variations in the dynamic behavior of the aircraft with changes in altitude. Using LMIs, the designed controller effectively adjusted the feedback gain matrix, ensuring performance under different flight conditions, and the closed-loop response demonstrated that the control system maintained a similar operating condition regardless of altitude.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This manuscript discusses the impacts of two factors on the results of a non-viscous CFD simulation of a combat aircraft: mesh refinement and the leading-edge sweep angle. Unlike viscous simulations, the non-viscous simulation of a delta wing with a rounded leading edge has a unique characteristic where mesh refinement consistently alters the flow topology, making mesh independence analysis ambiguous. To investigate this phenomenon further, the Generic Future Fighter, an aircraft initially devised by Linköping University and further studied in conjunction with Instituto Tecnológico de Aeronáutica, was used to validate this issue through aerodynamic coefficients obtained from wind tunnel tests from another work. Subsequently, using the mesh that yielded the most accurate results, the leading-edge sweep angle was varied while keeping the rest of the aircraft and other wing geometric parameters constant. The results of the first phase confirmed that mesh refinement progressively delays the separation of the leading-edge vortex. The results of the second phase were inconclusive, highlighting several points that require further investigation. The manuscript also presents a discussion on the highly nonlinear interaction between the canard vortex and the wing vortex, as well as the effect of the mesh on these interactions, an aspect lacking in recent studies which typically consider only a single lifting surface.

© 2024, Academia Brasileira de Ciencias. All rights reserved.Multirotors Aerial Vehicles are special class of Unmanned Aerial Vehicles with many practical applications. The growing demand for this class of aircraft requires tools that speed up their development. Simulated environments have gained increasing importance, as they facilitate testing and prototyping solutions, where virtual environments allow real-time interaction with simulated models, with similar behavior to real systems. More recently, the use of Augmented Reality has allowed an increasing experience of immersion and integration between the virtual world and a real scenario. This work proposes the use of Augmented Reality technology and a simulated model of a multirotor to create an interactive flight environment, aiming to improve the user experience in the analysis of simulated models. For this purpose, a smartphone was adopted as a hardware platform, a game engine is used as a basis for the development of the Augmented Reality application, that represents a numerical simulation of the flight dynamics and the control system of a multirotor, and a game controller is adopted for user interaction. The resulting system demonstrates that Augmented Reality is a viable technology that can be used to increase the possibilities of evaluating simulated systems.

©2024 Luiz Vitor Tozi, João Vidal, Jesuino Takachi Tomita, Anderson Vicente Borille, Cleverson Bringuenti, Alexandre Roma, Henrique Rodrigues Oliveira.The industry and the academy are continuously developing new technologies and approaches regarding the gas turbine manufacturing. Logically, sectors of turbomachinery and aerospace engineering are deeply focused on applying newer and even unconventional manufacturing process, aiming on cost reduction, reduced lead times and efficiency. In addition, it is conspicuous that metal additive manufacturing (AM) technologies can provide interesting possibilities for companies seeking to innovate and perfect existing components, with respect to reach better buy-to-fly ratios. In this paper, the authors developed a proposal for additively manufacturing a fuel swirler and evaluated in detail its process of fabrication in order to compare the results with the characteristic of a conventionally manufactured swirler. Furthermore, a dedicated review of the state-of-the-art related to the AM of fuel swirlers were realized to evaluate the relevance of this topic to conclude if the use of AM to fabricate this component can favor the aerospace industry.

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.This study focuses on 2D RANS (Reynolds Averaged Navier-Stokes) simulations using Spalart-Allmaras and k- ω SST turbulence models for a supersonic air inlet featuring two different passive control systems: an air bleed system in the external ramp of the inlet and a two-dimensional bump. The supersonic inlet serving to capture and decelerate the high-speed incoming flows is aerodynamically indispensable to an airbreathing supersonic aircraft. Sometimes, depending on the conditions of the entry flow, the shock wave boundary layer interaction (SWBLI) can lead to inlet unstart if not controlled, due to thickened boundary layer. To verify the impact of the passive control systems, the inlet was tested at freestream Mach number of 2.0 and 2.03 as the geometry is very sensitive to Mach number change. Results indicate that the air bleed system is more effective for Mach 2.0 and reduces the bubble size of approximately 80.0%. In the case of the two-dimensional bump, it was noticed that the bump should be placed after the impinging shock on the geometry. Even though the bubble size does not reduce as much as for the air bleed system, for the two-dimensional bump, the SWBLI is weakened.

© 2024 Elsevier B.V.We present a new linear eigensolution analysis technique that provides superior estimates of dissipation distribution in wavenumber space for the continuous Galerkin (CG) method. The technique builds upon traditional dispersion–diffusion analyses that have been applied to spectral/hp element methods, but in particular is an improvement upon the non-modal eigenanalysis approach proposed by Fernandez et al. (2019). The present technique takes into account the indirect effects that dispersion may have on dissipation, as recently discussed by Moura et al. (2022), in order to better represent dissipation itself. Also, a concept used by the dynamic mode decomposition (DMD) community is invoked to weight the relative contribution of the multiple diffusion curves that stem from temporal eigenanalysis. This allows for obtaining a single dissipation profile in wavenumber space, so that the proposed technique is named joint-mode analysis. Although the non-modal approach also provides a single diffusion curve, the joint-mode dissipation curve is shown to correlate significantly better with the energy spectrum of Burgers’ turbulence at large and intermediate scales, which is particularly relevant for implicit large-eddy simulation (LES). The proposed technique is readily extensible to other spectral/hp element methods.

© 2024 Elsevier Inc.We present a new linear eigensolution analysis technique that provides superior estimates of dissipation distribution in wavenumber space for the discontinuous Galerkin (DG) method. The technique builds upon traditional dispersion-diffusion analyses that have been applied to spectral/hp element methods, but in particular is an improvement upon the non-modal eigenanalysis approach proposed by Fernandez et al. in [1]. The present technique takes into account the indirect effects that dispersion may have on dissipation, as recently discussed by Moura et al. in [2], in order to better represent dissipation itself. Also, a concept often used with dynamic mode decomposition (DMD) techniques is invoked to weight the relative contribution of the multiple diffusion curves that stem from temporal eigenanalysis. This allows for obtaining a single dissipation profile in wavenumber space, so that the proposed technique is named joint-mode analysis. Although the non-modal approach also provides a single diffusion curve, the joint-mode dissipation curve is shown to correlate significantly better with the energy spectrum of Burgers' turbulence at large and intermediate scales, which is particularly relevant for implicit large-eddy simulation (LES). The proposed technique is readily extensible to other spectral/hp element methods.

© The Author(s), 2024.Guided-jet waves have been shown to close resonance loops in a myriad of problems such as screech and impingement tones in jets. These discrete, upstream-travelling waves have long been identified in linear-stability models of jet flows, but in this work they are instead considered in the context of an acoustic-scattering problem. It is shown that the guided-jet mode results from total internal reflection and transmission of acoustic waves, arising from the shear layer behaving like a duct with some given wall impedance. After total reflection, only discrete streamwise wavenumbers may be supported by the flow, with these wavenumbers dictated by the fact that the standing wave formed inside of the jet must fit between the two shear layers. Close to the sonic line, the transmission of this mode to the outside is maximum, leading to a net-energy flux directed upstream, which dictates the direction of propagation of this mode, providing a clear connection to the better understood soft-duct mode (Towne et al., J. Fluid Mech., vol. 825, 2017, pp. 1113-1152). The model also indicates that these waves are generated in the core of the flow and can only be efficiently transmitted to the quiescent region under certain conditions, providing an explanation as to why screech is only observed at conditions where the discrete mode is supported by the flow. The present results explain, for the first time, the nature and characteristics of the guided-jet waves.

© The Author(s), 2024. Published by Cambridge University Press.We present an experimental study of reactive control of turbulent jets, in which we target axisymmetric coherent structures, known to play a key role in the generation of sound. We first consider a forced jet, in which coherent structures are amplified above background levels, facilitating their detection, estimation and control. We then consider the more challenging case of an unforced jet. The linear control targets coherent structures in the region just downstream of the nozzle exit plane, where linear models are known to be appropriate for description of the lowest-order azimuthal modes of the turbulence. The control law is constructed in frequency space, based on empirically determined transfer functions. And the Wiener–Hopf formalism is used to enforce causality and to provide an optimal controller, as opposed to the sub-optimal control laws provided by simpler wave-cancellation methods. Significant improvements are demonstrated in the control of both forced and unforced jets. In the former case, order-of-magnitude reductions are achieved; and in the latter, turbulence levels are reduced by up to 60 %. The results open new perspectives for the control of turbulent flow at high Reynolds number.

© The Author(s), under exclusive licence to Springer Nature B.V. 2023.A comparative study of the acoustic far-field radiation of a subsonic jet near a folded plate with an opening, intended to represent a flapped wing with thrust gate, is presented in this work. Three openings with different widths were used to evaluate experimentally the influence of the gaps in the far-field noise radiation, for two folding angles. Boundary Element Method simulations with a wavepacket model which represents the jet acoustic source are used to calculate the far-field noise. Numerical simulation results are compared with experimental measurements and show similar trends in terms of acoustic radiation. Through parametric simulations, it was also possible to estimate that opening widths greater than one jet diameter do not contribute significantly to reducing the far-field noise. The results show that even the smallest tested openings were able to reduce the far-field noise for the tested positions.

© The Author(s), 2024. Published by Cambridge University Press.The low-frequency modal and non-modal linear dynamics of an incompressible, pressure-gradient-induced turbulent separation bubble (TSB) are investigated, with the objective of studying the mechanism responsible for the low-frequency contraction and expansion (breathing) commonly observed in experimental studies. The configuration of interest is a TSB generated on a flat test surface by a succession of adverse and favourable pressure gradients. The base flow selected for the analysis is the average TSB from the direct numerical simulation of Coleman et al. (J. Fluid Mech., vol. 847, 2018, pp. 28-70). Global mode analysis reveals that the eigenmodes of the linear operator are damped for all frequencies and wavenumbers. Furthermore, the least damped eigenmode appears to occur at zero frequency and low, non-zero spanwise wavenumber when scaled with the separation length. Resolvent analysis is then employed to examine the forced dynamics of the flow. At low frequency, a region of low, non-zero spanwise wavenumber is also discernible, where the receptivity appears to be driven by the identified weakly damped global mode. The corresponding optimal energy gain is shown to have the shape of a first-order, low-pass filter with a cut-off frequency consistent with the low-frequency unsteadiness in TSBs. The results from resolvent analysis are compared to the unsteady experimental database of Le Floc'h et al. (J. Fluid Mech., vol. 902, 2020, A13) in a similar TSB flow. The alignment between the optimal response and the first spectral proper orthogonal decomposition mode computed from the experiments is shown to be close to, while the spanwise wavenumber of the optimal response is consistent with that of the low-frequency breathing motion captured experimentally. This indicates that the fluctuations observed experimentally at low frequency closely match the response computed from resolvent analysis. Based on these results, we propose that the forced dynamics of the flow, driven by the weakly damped global mode, serve as a plausible mechanism for the origin of the low-frequency breathing motion commonly observed in experimental studies of TSBs.

© 2024 American Physical Society.Most of the studies on pressure fluctuations in wall-bounded turbulent flows aim at obtaining statistics as power spectra and scaling laws, especially at the walls. In the present study we study energetic coherent pressure structures of turbulent channel flows, aiming at a characterization of dominant coherent structures throughout the channel. Coherent structures are detected using spectral proper orthogonal decomposition (SPOD) and modeled using resolvent analysis, similarly to related works dealing with velocity fluctuations but this time using pressure fluctuations as the output of interest. The resolvent operator was considered with and without the Cess eddy-viscosity model. Direct numerical simulations (DNSs) of incompressible turbulent channel flows at friction Reynolds numbers of approximately 180 and 550 were employed as databases in this study. Three representative dominant structures emerged from a preliminary spectral analysis: near-wall, large-scale, and spanwise-coherent structures. For frequency-wave number combinations corresponding to these three representative structures, SPOD results show a strong dominance of the leading mode, highlighting low-rank behavior of pressure fluctuations. The leading resolvent mode closely agrees with the first SPOD mode, providing support to studies that showed better performance of resolvent-based estimators when predicting pressure fluctuations compared to velocity fluctuations [Amaral, J. Fluid Mech. 927, A17 (2021)JFLSA70022-112010.1017/jfm.2021.764]. The dominant mechanisms of the analyzed modes are seen to be the generation of quasistreamwise vortices with pressure fluctuations appearing close to vortex centers. A study on the individual contributions of the nonlinear terms (treated as forcing in resolvent analysis) to the pressure output reveals that each forcing component plays a constructive role to the input-output formulation, which also helps understanding the weaker role of forcing "color"in driving pressure fluctuations.

© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.Abstract: We study generalised quasilinear (GQL) approximations applied to turbulent plane Couette flow. The GQL framework is explored in conjunction with a Galerkin reduced-order model (ROM) recently developed by Cavalieri and Nogueira (Phys Rev Fluids 7:102601, 2022), which considers controllability modes of the linearised Navier–Stokes system as basis functions, representing coherent structures in the flow. The velocity field is decomposed into two groups: one composed by high-controllability modes and the other by low-controllability modes. The former group is solved with the full nonlinear equations, whereas the equations for the latter are linearised. We also consider a new GQL framework wherein the linearised equations for the low-controllability modes are driven by nonlinear interactions of modes in the first group, which are characterised by large-scale coherent structures. It is shown that GQL-ROMs successfully recover the statistics of the full model with relatively high controllability thresholds and sparser nonlinear operators. Driven GQL-ROMs were found to converge more rapidly than standard GQL approximations, providing accurate description of the statistics with a larger number of linearised modes. This indicates that the forcing of linearised flow structures by large-scale coherent structures is an important feature of turbulence dynamics that should be considered in GQL models. The results presented here reveal that further model reductions are attainable with GQL-ROMs, which can be valuable to extend these models to larger Reynolds numbers. Graphical abstract: (Figure presented.)

© The Author(s), 2024. Published by Cambridge University Press.We study the stability of a zero-pressure gradient boundary layer subjected to free-stream disturbances by means of local stability analysis. The dataset under study corresponds to a direct numerical simulation (DNS) of a flat plate with a sharp leading edge in realistic wind tunnel conditions, with a turbulence level of 3.45 % at the leading edge. We present a method to track the convective evolution of the secondary instabilities of streaks by performing sequential stability calculations following the wave packet, connecting successive unstable eigenfunctions. A scattered nature, in time and space, of secondary instabilities is seen in the stability calculations. These instabilities can be detected before they reach finite amplitude in the DNS, preceding the nucleation of turbulent spots, and whose appearance is well correlated to the transition onset. This represents further evidence regarding the relevance of secondary instabilities of streaks in the bypass transition in realistic flow conditions. Consistent with the spatio-temporal nature of this problem, our approach allows us to integrate directly the local growth rates to obtain the spatial amplification ratio of the individual instabilities, where it is shown that instabilities reaching an -factor in the range [2.5,4] can be directly correlated to more than 65 % of the nucleation events. Interestingly, it is found that high amplification is not only attained by modes with high growth rates, but also by instabilities with sustained low growth rates for a long time.

© The Author(s), 2024. Published by Cambridge University Press.Thin airfoil dynamic stall at moderate Reynolds numbers is typically linked to the sudden bursting of a small laminar separation bubble close to the leading edge. Given the strong sensitivity of laminar separation bubbles to external disturbances, the onset of dynamic stall on a NACA0009 airfoil section subject to different levels of low-amplitude free stream disturbances is investigated using direct numerical simulations. The flow is practically indistinguishable from clean inflow simulations in the literature for turbulence intensities at the leading edge of. At slightly higher turbulence intensities of, the bursting process is found to be considerably less smooth and strong coherent vortex shedding from the laminar separation bubble is observed prior to the formation of the dynamic stall vortex (DSV). This phenomenon is considered in more detail by analysing its appearance in an ensemble of simulations comprising statistically independent realisations of the flow, thus proving its statistical relevance. In order to extract the transient dynamics of the vortex shedding, the classical proper orthogonal decomposition method is generalised to include time in the energy measure and applied to the time-resolved simulation data of incipient dynamic stall. Using this technique, the dominant transient spatiotemporally correlated features are distilled and the wave train of the vortex shedding prior to the emergence of the main DSV is reconstructed from the flow data exhibiting dynamics of large-scale coherent growth and decay within the turbulent boundary layer.

© The Author(s) 2024.Abstract: This study presents a physics-based, low-order model for the trailing edge (TE) noise generated by an airfoil at low angle of attack. The approach employs incompressible resolvent analysis of the mean flow to extract relevant spanwise-coherent structures in the transitional boundary layer and near wake. These structures are integrated into Curle’s solution to Lighthill’s acoustic analogy to obtain the scattered acoustic field. The model has the advantage of predicting surface pressure fluctuations from first principles, avoiding reliance on empirical models, but with a free amplitude set by simulation data. The model is evaluated for the transitional flow (Re=5e4) around a NACA0012 airfoil at 3 deg angle of attack, which features TE noise with multiple tones. The mean flow is obtained from a compressible large eddy simulation, and spectral proper orthogonal decomposition (SPOD) is employed to extract the main hydrodynamic and acoustic features of the flow. Comparisons between resolvent and SPOD demonstrate that the physics-based model accurately captures the leading coherent structures at the main tones’ frequencies, resulting in a good agreement of the reconstructed acoustic power with that of the SPOD (within 4 dB). Discrepancies are observed at high frequencies, likely linked to nonlinearities that are not considered in the resolvent analysis. The model’s directivity aligns well with the data at low Helmholtz numbers, but it fails at high frequencies where the back-scattered pressure plays a significant role in directivity. This modeling approach opens the way for efficient optimization of airfoil shapes in combination with low-fidelity mean flow solvers to reduce TE noise. Graphical abstract: (Figure presented.)

© The Author(s), 2024. Published by Cambridge University Press.Plane Couette flow at Reynolds number Re = 1200 (based on the channel half-height and half the velocity difference between the top and bottom plates) is investigated with a spatial domain designed to retain only two spanwise integral length scales. In this system, the computation of invariant solutions that are physically representative of the turbulent state has been understood to be challenging. To address this challenge, our approach is to employ an accurate reduced-order model with 600 degrees of freedom (Cavalieri & Nogueira, Phys. Rev. Fluids, vol. 7, 2022, L102601). Using the two-scale energy budget and the temporal cross-correlation of key observables, it is first demonstrated that the model contains most of the multi-scale physical processes identified recently (Doohan et al., J. Fluid Mech., vol. 913, 2021, A8); i.e. the large- and small-scale self-sustaining processes, the energy cascade for turbulent dissipation, and an energy-cascade mediated small-scale production mechanism. Invariant solutions of the reduced-order model are subsequently computed, including 96 equilibria and 43 periodic orbits. It is found that none of the computed equilibrium solutions are able to reproduce an accurate energy balance associated with the multi-scale dynamics of the turbulent state. Incorporation of unsteadiness into invariant solutions is seen to be essential for a sensible description of the multi-scale turbulent dynamics and the related energetics, at least in this type of flow, as periodic orbits with a sufficiently long period are mainly able to describe the complex spatio-temporal dynamics associated with the known multi-scale phenomena.

© 2024 Author(s).The widest spanwise scales in turbulent channel flows are studied through the use of three periodic channel-flow simulations at friction Reynolds number Re τ = 550 . The length and height of the channels are the same in all cases ( L x / h = 8 π and L y / h = 2 , respectively), while the width is progressively doubled: L z / h = { 4 π , 8 π , 16 π } . The effects of increasing the domain width cannot be determined with statistical significance in our simulations, since the difference in the statistics between the simulations is of the same order as the errors of convergence. A channel flow similar to the smaller one [Del Álamo et al., “Scaling of the energy spectra of turbulent channels,” J. Fluid Mech. 500, 135-144 (2004)], which was averaged over a very long time, was used as a reference. The one-dimensional spanwise spectrum of the streamwise velocity is computed with the aim of assessing the domain-size effect on the widest scales. Our results indicate that 90% of the total streamwise energetic fluctuations is recovered without a significant influence of the size of the domain. The remaining 10% of the energy reflects that the widest scales in the outer layer are the ones most significantly affected by the spanwise length of the domain. The power-spectral density for kz = 0 remains constant even if the size of the domain in the spanwise direction is increased up to four times the standard spanwise length, indicating that wide, spanwise coherent structures are not an artifact of domain truncation.

© The Author(s) 2023.Abstract: An adjoint-based method is presented for determining manufacturing tolerances for aerodynamic surfaces with natural laminar flow subjected to wavy excrescences. The growth of convective unstable disturbances is computed by solving Euler, boundary layer, and parabolized stability equations. The gradient of the kinetic energy of disturbances in the boundary layer (E) with respect to surface grid points is calculated by solving adjoints of the governing equations. The accuracy of approximations of ΔE, using gradients obtained from adjoint, is investigated for several waviness heights. It is also shown how second-order derivatives increase the accuracy of approximations of ΔE when surface deformations are large. Then, for specific flight conditions, using the steepest ascent and the sequential least squares programming methodologies, the waviness profile with minimum L2-norm that causes a specific increase in the maximum value of N- factor, ΔN, is found. Finally, numerical tests are performed using the NLF(2)-0415 airfoil to specify tolerance levels for ΔN up to 2.0 for different flight conditions. Most simulations are carried out for a Mach number and angle of attack equal to 0.5 and 1.25∘, respectively, and with Reynolds numbers between 9×106 and 15×106 and for waviness profiles with different ranges of wavelengths. Finally, some additional studies are presented for different angles of attack and Mach numbers to show their effects on the computed tolerances. Graphic abstract: (Figure presented.).

© The Author(s), 2024. Published by Cambridge University Press.Large-eddy simulations of a flat-plate boundary layer, without a leading edge, subject to multiple levels of incoming free-stream turbulence are considered in the present work. Within an input–output model, where nonlinear terms of the incompressible Navier–Stokes equations are treated as an external forcing, we manage to separate inputs related to perturbations coming through the intake of the numerical domain, whose evolution represents a linear mechanism, and the volumetric nonlinear forcing due to triadic interactions. With these, we perform the full reconstruction of the statistics of the flow, as measured in the simulations, to quantify pairs of wavenumbers and frequencies more affected by either linear or nonlinear receptivity mechanisms. Inside the boundary layer, different wavenumbers at near-zero frequency reveal streaky structures. Those that are amplified predominantly via linear interactions with the incoming vorticity occur upstream and display transient growth, while those generated by the nonlinear forcing are the most energetic and appear in more downstream positions. The latter feature vortices growing proportionally to the laminar boundary layer thickness, along with a velocity profile that agrees with the optimal amplification obtained by linear transient growth theory. The numerical approach presented is general and could potentially be extended to any simulation for which receptivity to incoming perturbations needs to be assessed.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.We aim to reduce the noise emitted by high-speed turbulent jets using recently developed resolvent-based estimation and control tools. Our approach relies on detecting noise-generating wavepackets and canceling them via actuation. This paper reports on our progress toward this objective in the form of (i) implementation and validation of these resolvent-based tools in a large-scale CFD solver and (ii) preliminary estimation results for a subsonic jet. We validate our implementation via comparisons to the literature for a laminar channel flow, the acoustic response to a monopole forcing in a freestream, a trailing-line vortex problem, an airfoil wake, and resolvent modes for a jet. The preliminary estimation study for the subsonic jet shows that operator-based and data-driven versions of the methods yield similar estimation kernels and results. Future work will focus on extending this study to a series of supersonic jets and systematically exploring the selection and placement of sensors, actuators, and targets to mitigate noise-generating wavepackets most effectively

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.We present the results from a physics-based model of the trailing-edge (TE) noise radiated by an airfoil, obtained from resolvent analysis of the turbulent mean flow. In our approach, the acoustic model input is reduced to the optimal coherent structures identified by the resolvent. This method has the advantage of isolating the main mechanisms generating noise in the turbulent flow and, unlike empirical models, is applicable to a wide variety of cases. We investigate a NACA0012 airfoil at 3 deg angle of attack, equipped with a zigzag trip to trigger a turbulent boundary layer, which results in broadband TE noise. The analysis is based on a large eddy simulation (LES) for a chord-based Reynolds number Re = 2.105 . The time-averaged flow is used to construct the linear operator underlying resolvent analysis, and a spectral proper orthogonal decomposition (SPOD) of the snapshots is used to extract the main hydrodynamic and acoustic features of the flow, used as a reference for the resolvent model. The results demonstrate that the resolvent-based model can accurately reproduce both the coherent structures associated with TE noise and the directivity of the radiated sound field when low-rank dynamics are identified with SPOD. Although the region of low-rank dynamics corresponds to the peak of acoustic power, a significant portion of the spectrum is associated with high-rank dynamics, which we do not attempt to model here. Nevertheless, the resolvent model identifies a wavepacket on the suction side of the trailing edge as the main driver of TE noise, and allows us to investigate spanwise wavenumbers which are not resolved in the LES.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The dynamics of wavepackets in an elliptical jets are studied using direct numerical simulation (DNS) data of an AR = 2 incompressible elliptical jet at Reynolds number Re = 400. Analysis of the numerical data displays several complex features, the most striking being axis switching, a phenomenon that strongly affects the development of coherent structures in the flow. By applying spectral proper orthogonal decomposition (SPOD), it was found that modes in the SA symmetry were dominated by the Se1 flapping geometry in the upstream region. After the axis-switching point, the mode structure becomes more complex and multi-modal at mid-frequencies, while the mode structure remains largely unchanged for very low frequencies. Linear parabolised stability equations (PSE) are also used to evaluate the development of the different Kelvin-Helmholtz wavepackets in this elliptical jet showing excellent agreement with the SPOD modes.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Upstream-travelling guided jet waves have been shown to be one of the key elements in many resonance processes underpinned in high-speed jets. Despite its importance, many of its characteristics, including how these waves are generated and how it can travel subsonically, have not been detailed in the literature. In this work, we aim to provide a clarification about the dynamics of this mode. With the aid of an acoustic scattering formulation, we are able to show that the guided-jet mode results from total-internal-reflection and transmission to decaying waves, arising from the shear layer behaving like a hard duct. After total reflection, only discrete streamwise wavenumbers may be supported by the flow, with these wavenumbers dictated by the fact that the standing wave formed inside of the jet must fit between the two shear layers. Close to the sonic line, the transmission of this mode to the outside is maximum, leading to a net-energy flux directed upstream, which dictates the direction of propagation of this mode in the eigenspectrum, providing a clear connection to the better understood soft-duct mode.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The present paper is a follow up of a previous study on the effect of streaky-generating cylindrical tabs located on the inner surface of a round nozzle on jet aeroacoustics (Amaral et al., AIAA AVIATION 2023 Forum, p. 4516, 2023). The aim is to identify coherent structures through stereoscopic particle image velocimetry (stereo PIV) measurements obtained in crossstream planes parallel to the jet nozzle exit. As the tabbed nozzle has L-fold symmetry, Floquet exponents are used to perform Fourier decomposition in the azimuthal direction. Spectral proper orthogonal decomposition (SPOD) is employed to extract coherent structures. Comparison of the structures obtained for nozzles with and without tabs show the strong enhancement of streaks produced by the tabbed nozzle.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.In the last few years, flow control has become increasingly important for the aeronautical field, since it is seen as a promising tool to design safer and more efficient aircraft. In this regard, noise emission is still a major concern in the aviation industry. Specifically, for the under-wing configuration currently adopted in civil aircraft. When the jet interacts with a nearby surface, such as the wing, hydrodynamic structures are scattered into the acoustic field, drastically increasing the emitted noise. Within this context, a feed-forward control scheme is considered for the attenuation of jet installation noise in the far field. Since non-causality is observed in several flow control problems solved in the frequency domain, we compare a wave-cancelling approach, where causality is imposed via the truncation of the control kernel, to the Wiener-Hopf approach, where the causality constraint is imposed a priori. The latter provides an optimal causal solution, and with this, prevents the drop in performance that may be observed in flow control applications that use a truncated solution. The results presented here show a significantly better performance of the Wiener-Hopf method with respect to that of a truncated Kernel, where the control was performed based on microphones measurements, which provided the axisymmetric mode in the near field of the jet as the input signal for the controller. An attenuation of up to 5dB of the broadband spectral hump related to installation effects is obtained.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Coherence decay has been understood to be a key quantity to predict acoustic noise emitted by wavepackets in subsonic turbulent jets. Frequency-domain frameworks such as input-output and resolvent analyses are able to predict accurately the spatial structure of wavepackets turbulent flows compared to coherent structures educed from simulation data (as for example identified using spectral proper orthogonal, SPOD). However, at least at reduced-order, they are unable to capture two-point statistics such as coherence. A missing piece is the modelling of variability induced by the turbulence, which jitters (disorganises) the coherent structures and leads to stronger noise radiation. The aim of the present study is to consider the impact of turbulence on jet wavepackets through stochastic modelling under location uncertainty. This framework considers the conservation of mass and momentum of fluid parcels submitted to a stochastic transport, representing here the effect of turbulence. By linearising the resulting generalised stochastic Navier–Stokes equations and expressing it in the Fourier domain, a stochastic linear model (SLM) is obtained. We explore in this paper that ability of SLM to predict the two point coherence of the wavepackets in turbulent jets, and show its impact on acoustic emissions.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.A current area of interest within jet noise is the installed-jet configuration, being a representation of interactions between the aircraft exhaust and the wing. This work considers a previously presented dataset (Amaral et al. AIAA paper 2023-3830) where a simplified configuration involving a round jet and a rectangular plate was studied, and explores the different tonal regimes that are observed across jet Mach number and plate radial offset (R/D) for constant plate axial offset and angle. These are, broadband, transitional, linear frequency-selection (LFS), LFS with non-linearities, and non-linear frequency-selection (NLFS). Results also suggested a transition from LFS to NLFS tone as R/D is decreased, and that for the case of NLFS, triadic interactions between two frequencies may produce all other tones within the spectrum.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The aim of present work is to investigate trailing-edge noise generation mechanisms to improve prediction tools and control strategies. We focus on a NACA 0012 airfoil at 3 degrees angle of attack with zigzag tripping elements close to the leading edge to generate a turbulent boundary layer. A compressible implicit large eddy simulation (LES), using the open-source high-order numerical framework PyFR, is performed for collecting data for our analysis. For comparison, we use data from an experimental campaign performed in parallel at the facility in TU Berlin. The comparison of velocity and sound pressure statistics shows good agreement between simulations and experiments. Further, spectral proper orthogonal decomposition (SPOD) is applied to the LES dataset to investigate dominant feature of the turbulent boundary layer and its relation to sound radiation. SPOD analysis is applied to different spanwise wavenumbers in order to understand their contribution to noise generation. Leading SPOD modes for the first spanwise wavenumbers, which dominate acoustic radiation, are shown to correspond to wavepackets. The contribution of such coherent structures in the radiated sound field is examined, clarifying their contribution to trailing-edge noise for a wide range of frequencies.

© 2024 International Forum on Aeroelasticity and Structural Dynamics, IFASD 2024. All rights reserved.The renaissance of neural networks in the scientific community in recent years has brought new perspectives for improving the computational efficiency of traditional modeling techniques. Hamiltonian neural networks leverage the energy-preserving properties of the Hamiltonian formalism to provide surrogate models with increased interpretability compared to conventional feed-forward models. In this study, we employ a lumped-mass multibody method to derive the equations of motion of two highly flexible structures. We perform a model order reduction via modal decomposition while preserving the nonlinearities with the use of exact kinematic relations. After validating full- and reduced-order models, we use them to produce datasets and train the neural networks, which serve as ready-to-use surrogate models. Preliminary findings show that the surrogate models based on neural networks can significantly reduce the time necessary to simulate the free response of the structures. Furthermore, we demonstrate that surrogate models based on Hamiltonian neural networks have energy-preserving capabilities, maintaining accuracy levels even for long simulations. Due to their architecture, when external loads are considered, the surrogate models require the analytical calculation of the generalized forces, jeopardizing the efficiency gains obtained by our approach. We also present initial findings on the use of neural networks for faster aerodynamic models for flexible aircraft, particularly as surrogate models for the vortex-lattice method. By using a neural network as the aerodynamic surrogate model in a specific flexible aircraft simulation framework, the computational costs were reduced by a factor of 100 on average. The outcomes of this study demonstrate that surrogate models based on neural networks can soon become an efficient and reliable alternative for modeling arbitrarily flexible aircraft, provided the current limitations are addressed.

© 2024 by the authors.We report a joint high-pressure experimental and theoretical study of the structural, vibrational, and photoluminescent properties of pure and Eu3+-doped cubic Y2O3 nanoparticles with two very different average particle sizes. We compare the results of synchrotron X-ray diffraction, Raman scattering, and photoluminescence measurements in nanoparticles with ab initio density-functional simulations in bulk material with the aim to understand the influence of the average particle size on the properties of pure and doped Y2O3 nanoparticles under compression. We observe that the high-pressure phase behavior of Y2O3 nanoparticles depends on the average particle size, but in a different way to that previously reported. Nanoparticles with an average particle size of ~37 nm show the same pressure-induced phase transition sequence on upstroke and downstroke as the bulk sample; however, nanoparticles with an average particle size of ~6 nm undergo an irreversible pressure-induced amorphization above 16 GPa that is completed above 24 GPa. On downstroke, 6 nm nanoparticles likely consist of an amorphous phase.

© 1973-2012 IEEE.This study employed an inverted reactor approach to activate tap water (TW) using effluent bubbles derived from a gliding arc discharge (GAD). Optical emission spectroscopy (OES) analysis revealed the dominant presence of nitrogen species and oxygen radicals within specified spectral ranges. The physicochemical attributes of the plasma-activated TW (PATW) remained consistent, highlighting the efficacy of the reactor's bubbling system. Through UV-Vis spectrophotometry and pH analysis, the notable observation was the stabilizing influence of hydrogen peroxide (H2O2) and positive hydrogen ions (H+) during the initial activation phases (75 min), which played a significant role in maintaining mildly alkaline pH. Energy efficiency metrics demonstrated a decline up to 1.25 h of activation, with subsequent stabilization. Our research outcomes further emphasize the efficacy of GAD, shedding light on its significant potential in optimizing the water activation process.

© 2024, Escola de Minas. All rights reserved.A Hollow Cathode Plasma Enhanced Chemical Vapor Deposition (HC-PECVD) reactor was used to deposit silver doped Diamond-Like Carbon (Ag-DLC) films on Ti6Al4V alloy employing two methodologies: i) producing a silicon interlayer, using tetramethylsilane (TMS) as silicon precursor, varying the argon flow of the hollow cathode; and ii) carbonitriding the substrate. Profilometry, Raman, and Secondary Ion Mass Spectrometry (SIMS), as well as nanohardness, micro-scratch, scratch, and VDI 3198 indentation tests were used to evaluate the characteristics of the films and their adhesion on the substrates. The results demonstrated that the argon flow can be used for tuning the Ag-DLC film’s hardness, toughness, and adherence on silicon interlayers. The carbonitriding process, in turn, provided an improvement in the film toughness compared with non-carbonitrided samples. Considering the lower cost and easier handling of N2 compared to the silicon precursors commonly available (TMS, HDMSO, SiH4, etc.), the carbonitriding process proved more appropriate to improve the adhesion of the Ag-DLC films on the Ti6Al4V alloy.

© 2024The aviation industry accounts for part of the CO2 emissions contributing to climate change. The industry has established a target to reduce 2050 net aviation carbon emissions by 50 % relative to 2005 levels. With this in mind, waste heat recovery is a key pathway to achieve reduced emissions and improve system efficiency. The waste heat may potentially be converted to electric power using a supercritical CO2 Brayton power cycle. The sCO2 power system offers the advantage of compactness owing to the high working fluid density, which is an important consideration for aircraft performance. The present work focuses on the integration of the sCO2 power system into the aircraft propulsion system and evaluation of its performance. Detailed optimization of the sCO2 waste heat system will be evaluated with a focus on cycle efficiency and net power under different operating conditions, including ground, takeoff, climb, cruise, and landing operations. The study is divided into two parts with two different turbofan engines, one with a nominal thrust of 30 kN and the other with a nominal thrust of 9 kN. The first part shows the effect and operation of the waste heat recovery unit under the different operating conditions. The second part is focused on cycle optimization and performance evaluation. The results demonstrate the potential of waste heat recovery during a range of operational conditions. The sCO2 cycle efficiency can reach between 25 and 39 % (depending on aircraft engine) with net power output in the range of 100 to 260 kW.

© 2024 Elsevier LtdThe global increase in food demand drives the need for efficient and sustainable agricultural practices, particularly in the energy-intensive process of grain drying, which is crucial for maintaining product quality. This study proposes the exergetic and environmental analysis of a hybrid electric column dryer for soybeans, comparing its performance across four distinct national contexts: Paraguay, Brazil, the United States, and China. The aim is to explore how different energy matrices and degrees of hybridization influence the energy and environmental costs associated with soybean drying. In addition to considering different energy matrices, the present study advances beyond previous research by coupling the mathematical drying model with thermodynamic analysis. By integrating these aspects, it is possible to conduct thorough simulations and gain insights into the exergetic, environmental, and economic impacts of the drying process. For this, a computational model was developed capable of simulating the drying process of soybeans and determining the conditions of grains and air at the exit of the drying chamber and, thus, performing the First and Second Law analyses with different degrees of hybridization for four countries with different electricity mixes. Results reveal that for thin-layer soybean drying dynamics at T = 80 °C and v = 0.5 m/s, approximately 68.2 min were needed to reduce grain moisture content from 18% w.b (0.22 d.b) to 14% (0.163 d.b), with outlet temperatures of θ = 67.57 °C for grains and T = 71.7 °C for air. The final water content of the drying air was 0.021 kgw/kga. Exergetic cost analysis revealed significant variations among countries, with Paraguay exhibiting the greatest difference between completely fossil and purely electrical cases (433.5 kJ/kgg). Environmental cost analysis showed substantial differences in electrical energy use for drying, particularly in countries with predominantly renewable energy matrices. Paraguay showed the highest emissions variation with a purely electrical system, differing by 27.55 gCO2/kgg compared to the pure fossil case. Brazil, the United States, and China had differences of 25.33, 17.4, and 11.90 gCO2/kgg, respectively. From an economic standpoint, hybridization was found to be unfeasible in Brazil due to high electricity prices, while theoretically favorable in China, Paraguay, and the United States. Paraguay had the lowest drying cost at 2.63 US$/tong, followed by China, the United States, and Brazil with 3.92, 4.74, and 15.79 US$/tong, respectively. These analyses underscore the importance of comprehensive studies in evaluating process hybridization. Considering electricity mix composition and reliable life cycle analysis data is crucial for obtaining meaningful results. Integrated exergetic, environmental, and economic analyses are essential for guiding energy use decision-making processes.

© 2024 by the authors.The internal losses in the tip clearance region strongly influence the compressor performance and its operational range. Previous research proved that passive wall treatments with circumferential grooves in axial compressors effectively increase the compressor stall margin. The vortex generated inside the circumferential grooves creates a resistance to the flow that leaks into the tip clearance region of the compressor. However, most works found in the literature on circumferential grooves in axial compressors deal only with high-performance single-stage axial compressors. Therefore, there is a need to investigate and analyze the behavior of circumferential grooves in a multi-stage environment. In the present work, a passive wall treatment with circumferential grooves was implemented in a multi-stage axial compressor. Different configurations of circumferential grooves were created at the casing of the first and second rotor rows used in a four-stage axial flow compressor. Numerical simulations were performed to evaluate the influence of the circumferential grooves on the performance of a multi-stage axial compressor. The results obtained after the simulations for the different circumferential groove configurations were compared with the results obtained for the compressor without casing treatment (smooth wall) for different rotational speeds. Furthermore, the complete compressor map characteristics were simulated for the different casing treatment configurations, and the results were compared with the compressor characteristics of the smooth wall case. The passive wall treatment with circumferential grooves produced changes in the multi-stage axial compressor flow field, especially in the tip clearance region, improving the compressor stability mainly for part load speeds.

© 2024 Tiago Andrei Adamczevski, Luiz Vitor Tozi, João Guilherme Vidal do Nascimento, Cleverson Bringhenti, Jesuíno Takachi Tomita.This paper presents the development of a gas turbine simulator based on an application of a real turbogenerator used to generate electricity on an offshore oil platform, the configuration is a turboshaft with free power turbine. The compressor, turbines and the control system were developed using specific methodologies. The development of the simulator was done using the Simulink environment in Matlab®. The development was done using blocks to represent each one of the main components in the engine. A stage stacking methodology based on the real geometry for each stage was adopted to create the compressor maps. The map was used in lookup tables blocks with help of auxiliary coordinates, also known as beta lines. To model both turbines were applied an ellipse equation also known as Stodola’s law. The engine simulator model was tested in an open loop and the results evaluated with the manual data from the engine.

© 2024 by the authors.The ratio between blade height and chord, named the aspect ratio (AR), plays an important role in compressor aerodynamic design. Once selected, it influences stage performance, blade losses and the stage stability margin. The choice of the design AR involves both aerodynamic and mechanical considerations, and an aim is frequently to achieve the desired operating range while maximizing efficiency. For a fixed set of aerodynamic and geometric parameters, there will be an optimal choice of AR that achieves a maximum efficiency. However, for a state-of-the-art aero-engine design, optimality means multi-objective optimality, that is, reaching the highest possible efficiency for a number of operating points while achieving a sufficient stability margin. To this end, the influence of the AR on the performance of the first rotor row of a multistage, multi-objective, high-speed compressor design is analyzed. A careful setup of the high-speed aerodynamic design problem allows the effect of the AR to be isolated. Close to the optimal AR, only a modest efficiency variation is observed, but a considerable change in compressor stability margin (SM) is noted. Decreasing the AR allows for increasing efficiency, but at the expense of a reduced surge margin. This allows the designer to trade efficiency for stability. Increasing the AR, however, is shown to reduce both the surge margin and efficiency; hence, a distinct optimality in stability is observed for the analyzed rotor blade row. In this work, optimality in the surge margin with respect to the AR is observed, whereas there is a close to optimal efficiency. The predicted range from AR = 1.10 to AR = 1.64 is only indicative, considering that the definition of multi-objective optimality requires balancing efficiency and the surge margin and that the choice of balancing these two criteria requires making a design choice along a pareto optimal front.

© 2024 by ASME.This work aims to provide a methodology for defining the design point for industrial gas turbine considering the economic, environmental, and engine performance aspects. The definition of the design point is a key step in the development project of a gas turbine since this definition involves the analysis of several operational points to verify if the desired performance can be obtained. Thus, to extend the methodology presented in the literature developed for micro-turbines to consider industrial gas turbines a computer program was developed in MATLAB®. This program is capable of performing thermodynamic calculations for design point definition and of performing single- and multi-objective thermoeconomic and thermodynamic optimizations using genetic algorithms. For the optimization process, total cost minimization, yield maximization, and gas turbine-specific work maximization were chosen as objective functions. The decision variables chosen were compressor pressure ratio, compressor polytropic efficiency, turbine polytropic efficiency, and maximum cycle temperature. For the calculation of economic aspects, fixed costs (equipment, installations, land acquisition cost, etc.) and variable costs (fuel, emissions, and operation and maintenance costs) were considered. The emission cost of NOx, CO, and UHC was considered for the environmental cost calculations. The thermodynamic calculations were based on enthalpy and entropy. The developed computer program was validated by simulating a commercial gas turbine and comparing the results obtained, also using a commercial program, GASTURB®. The presented optimization process shows results for a single objective, two objectives, and three objectives, where the results show a comparison between different design points obtained. The software developed will be of great assistance in the learning of engineering students.

© 2024 by ASME.The air conditioning system of executive, commercial, or military aircraft heavily relies on air cycle machines due to the availability of engine bleed air and their lightness and reliability compared to vapor cycle systems. The type of application, weight, refrigeration capacity, financial aspects, size, performance, and other specific design requirements drive the selection of suitable equipment for a particular aircraft. The motivation of this paper has been based on summarize the main concepts of the aeronautical environmental control system, as well as the mathematical aspects underlying the modeling of a simple/bootstrap air cycle unit in a software. The main aim is to develop software that can generate high level requirements that would be refined during the development phase of an aeronautical air conditioning system. It will be greatly benefit for engineers and students in the design of aeronautical air conditioning systems to better understand and to meet the design requirements. The results demonstrate the influence of the water-sprayer and chilled-recirculation system on air cycle performance and cabin inlet temperature, respectively. They also show changes in certain parameters of interest such as a function of altitude, power consumed by the secondary compressor, and air cycle machine fan. The computational model has proven to be a useful tool for performing parametric studies and evaluating critical points in designing and selecting an air conditioning unit based on a simple/bootstrap air cycle with humid air (any quantity of moist) as the working fluid.

© 2024 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.Decarbonization of the aviation sector is a key factor for current and future systems. Waste Heat Recovery (WHR) may be used to convert waste energy to electric power by using a bottoming cycle, which can reduce the overall fuel requirement of the airplane. One of the potential bottoming cycles for aircraft application is a Supercritical CO2 (sCO2) power system. The sCO2 power system has advantages because of the component compactness, which is crucial for aircraft integration. However, the main challenge for aircraft integration is the size and weight of the heat exchangers. The present work focuses on the performance of the Supercritical CO2 power system in both current and next-generation aircraft engines considering an innovative and advanced design of the sCO2 heat exchangers (cooler and primary heat exchanger). The first part of the work is focused on the analysis of the sCO2 WHR system for an aircraft engine. The second part of the work is focused on a detailed heat exchanger selection, design and optimization based on the aircraft engine parameters. The results show the potential of WHR utilization, which may generate an additional 100 - 200 kW. However, the heat exchangers may increase overall weight of the aircraft. For this reason, an advanced design is necessary.

© 2024, ETA-Florence Renewable Energies. All rights reserved.The green hydrogen industry is gaining momentum globally as a carrier of clean, sustainable energy with the potential to significantly reduce greenhouse gas emissions. Brazil, with its vast renewable energy resources and commitment to decarbonization, is emerging as a promising player in the green hydrogen market. As Brazil’s green hydrogen infrastructure expands, ensuring the safety and reliability of pipelines and accessories becomes crucial. This research provides an overview of the state of the art in pipeline and accessory inspection processes in the green hydrogen industry in Brazil, highlighting the advances and challenges faced in this rapidly evolving sector. It can also contribute to a better understanding of current knowledge about inspections in the green hydrogen transport network and how the collaboration of actors involved in the process of building international and national scientific knowledge is being carried out.

© Brazilian Society for Automatics--SBA 2024.This paper is concerned with the translational guidance of multirotor aerial vehicles with uncertain dynamics and equipped with short-range detection sensors in a scenario containing disturbances/uncertainties, multiple accelerated obstacles, and velocity constraints. To address this problem, we propose a robust guidance strategy based on the continuous control obstacles method. To handle disturbances and uncertainties, the proposed method tightens the position and velocity admissible sets according to the respective tracking errors. Moreover, a hybrid prescribed-time arbitrary-order differentiator is employed to robustly estimate the obstacles’ velocities and accelerations within a prescribed time interval using measurements from a short-range sensor. As a result, the proposed method can fit into the available time for executing an avoidance maneuver upon the detection and tracking of obstacles. Then, we build a set of possible future positions for the obstacles according to their observed velocities and accelerations, and use this set to calculate a position command for the guided vehicle. The proposed method is experimentally evaluated using an augmented-reality setup composed of a Crazyflie quadcopter, motion capture cameras, and virtual obstacles. The results show that the proposed method is viable for real-time implementation and effective in providing collision avoidance and satisfying velocity constraints.

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.This paper is concerned with the design and analysis of the three-dimensional attitude control law of an arbitrary underactuated multirotor aerial vehicle with a fully actuated three-axis attitude motion subject to bounded matched disturbances and uncertainties, both with unknown bounds. To tackle the problem, the rotational kinematics and dynamics of the attitude and angular velocity control errors are first modeled in a geometrically consistent form using the Gibbs vector. Then, we formulate a multi-input adaptive sliding mode control strategy, of the unit-vector type, based on an increasing switching-gain adaptation law. The adaptive switching gain is proved to converge to its maximum bound, even in the presence of sufficiently small chattering, and the existence of an eventual sliding mode is assured. The method is extensively evaluated by simulation considering an X-shaped octa-rotor aerial vehicle. It is also demonstrated experimentally using a three-axis hover that emulates a quadrotor aerial vehicle.

© 2024 IEEE.This paper deals with the robust prescribed-time nonlinear state estimation for fusing multiple redundant noisy sensor measurements. Firstly, we present the prescribed-time super-twisting algorithm (PT-STA), which is a recent modified version of the classical super-twisting algorithm that ensures robust convergence within a prescribed time. Subsequently, the PT-STA is used to design a prescribed-time nonlinear robust state observer for second-order systems subject to disturbances and uncertainties. The observer is then combined with an average-based sensor fusion strategy that further improve the overall estimates in terms of noise rejection and sensor fault tolerance. We introduce sensor fusion algorithm for considering the availability of multiple redundant measurements. The effectiveness of the proposed scheme is illustrated via numerical simulations of a perturbed damped pendulum, under different numbers of measurements and also considering sensor fault. We compare the results with those obtained using the conventional super-twisting observer. The results indicate robust convergence of estimation errors to the origin within the prescribed time, a reduction in measurement noise as the number of measurements is increased, and sensor fault tolerance.

© 2024 IEEE.This paper proposes a robust guidance for mul-tirotor aerial vehicles with uncertain dynamics and equipped with short-range detection sensors in scenarios with multiple accelerated obstacles and velocity constraints. To handle the uncertain dynamics in the guidance level, the position and velocity admissible sets are tightened according to the respective inner-loop tracking errors. Moreover, a hybrid prescribed-time arbitrary-order differentiator is used to estimate the obstacles' velocities and accelerations using the sensor readings. Based on these estimates, we build a set of possible future positions for the obstacles, and use this set to calculate a robust collision-free position command for the vehicle. The proposed method is experimentally evaluated using a mixed-reality setup composed of a Crazyflie quad copter, motion capture cameras, and virtual obstacles. The results show that the proposed method is viable for real-time implementation and effective in providing collision avoidance and satisfying velocity constraints.

© 2024 IEEE.The control allocation of a quad copter with I-DOF vectoring thrust, respecting the rotors and actuators' physical bounds, is the subject of this paper. We start by assuming a hierarchical control architecture, where the control law gen-erates resultant force and torque commands to be distributed by the control allocation algorithm among the spinning and thrust vectoring motors. We define the control allocation as an optimization problem with the thrust vector components of each rotor being the design variables. By doing so, we obtain a set of constraints that depend linearly on the thrust vector magnitudes. The magnitude constraints can lead to a non-convex set when the rotors' minimum speed command is greater than zero. We tackle this issue by defining a conservative inferior limit to one of the thrust components in a way that the non-convexity is excluded from the resulting constraint set. To ensure the feasibility of the method, we state that the control effort commands outputted by the vehicle control law must lie within an admissible set of that optimization problem. Simulation results compared the proposed method with other control allocation strategies and showed that it is more effective in preventing violations of rotor constraints while achieving the required command of resulting force and torque.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.The present paper is concerned with the robust attitude-position tracking control for a formation of heterogeneous fully actuated multirotor aerial vehicles equipped with fixed rotors and subject to matched model uncertainties and Lipschitz disturbances. Based on a geometrically consistent description of the control error in SE(3), a joint geometric attitude-position control law is designed using a super-twisting sliding mode approach. Trajectory commands for the formation are generated using a second-order polynomial S-curve model, which are designed in such a way that allow setting different time duration for the formation acquisition, position, and attitude commanded motions. The method is evaluated via numerical simulations using a formation of non-planar fully actuated hexacopters equipped with fixed rotors, showing to be effective and simple to implement and tune.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.This work is concerned with the attitude and position control of a fully actuated non-planar hexarotor aerial vehicle equipped with reversible fixed rotors. The complete nonlinear dynamics of the vehicle is modeled in a state error formulation with six degrees of freedom (DOF), being three for position and three others for attitude, while the control input is also a six-DOF quantity defined in terms of the resultant force and torque acting on the system. A control law is designed using an unit-vector global sliding mode control strategy, which ensures robustness against bounded force and torque disturbances during the entire flight since the sliding condition is guaranteed from the initial time. Furthermore, the proposed controller also ensures global exponential stability for both the closed-loop translational and rotational dynamics. Using computational simulations, the designed control law is compared with an inverse-dynamic stabilizing control, showing to be effective and to perform much better.

© 2013 IEEE.This paper addresses the robustness of a novel two-stage super-twisting algorithm designed to converge within a prescribed time interval despite disturbances and model uncertainties. Initially, we introduce a method for tuning parameters that guarantees the algorithm's analytic solution will reach the origin precisely at a prescribed instant, assuming an unperturbed scenario. We then enhance this method to maintain prescribed-time convergence, even when faced with unknown bounded disturbances. The algorithm's performance is demonstrated through a numerical simulation of a state estimation problem for a perturbed damped pendulum. The results show that the estimation errors converge robustly to the origin at the prescribed time and remain there afterward.

© 2013 IEEE.This paper is concerned with the attitude and position control of underactuated multirotor aerial vehicles in the presence of matched disturbances and uncertainties, using the hierarchical scheme that nests the attitude control loop inside the position one. It is well-known that the effectiveness of this scheme depends on a proper control tuning for achieving a sufficient time-scale separation (TSS) between the closed-loop (faster) rotational and (slower) translational dynamics. However, a TSS cannot be ensured under an ideal sliding mode position control law since the attitude command, computed from the position control signal, is infinitely fast. The present paper tackles this problem in a way to enforce TSS without losing robustness and using a dull trial-and-error tweak of gains. That is achieved by designing, on the one hand, a new adaptive integral sliding mode attitude control law (AISMAC) that, under a sufficient smooth attitude command, ensures the existence of an attitude sliding mode during all the time, including the adaptation phase, thus allowing an infinitely fast inner loop. On the other hand, the outer loop is equipped with a disturbance-observer-based proportional-derivative position control law that ensures the required smoothness of the attitude command and provides robustness with respect to unknown force terms. The proposed design is extensively evaluated in a realistic simulator and shows to effectively enforce the TSS.

© 2024 Elsevier Masson SASTransonic flows at high Reynolds numbers can lead to high dynamic pressures and, consequently, to aerostructural deflections of aircraft structures. This study aims to develop and validate a high-fidelity static aeroelastic analysis environment that is efficient and that can be used in an industrial setting. The aerodynamics is represented by numerical solutions of the Reynolds-averaged Navier-Stokes equations with appropriate turbulence closures. The load transfer process uses finite element shape functions in order to distribute the aerodynamic loads into the structural discretization. The structural analysis employs a modal basis approach, and a wingtip deflection convergence study is performed to find an adequate modal basis size. Radial basis functions are used for the fluid mesh displacement, and the influence of the support radius is evaluated to determine the optimal values relative to the wing mean aerodynamic chord. The capability is tested using the static aeroelastic benchmarks of the High Reynolds Aerostructural Dynamics Project (HIRENASD) and NASA's Common Research Model (CRM). The static aeroelastic results demonstrate robustness and consistency for the aerodynamic coefficients, pressure distributions, and structural deflection predictions at different normalized dynamic pressure values and grid refinement levels.

© 2024 Elsevier LtdCarbon nanotube fibers or yarns (CNTYs) are lightweight, stiff, strong, electrically, and thermally conductive fiber-like materials that exhibit a piezoresistive response and could be integrated in glass-fiber/epoxy laminated composite materials to measure strain and to detect damage. Aiming at extending the scope of previous studies, this work is about the piezoresistive response of CNTY sensors integrated in composite laminates of industrial interest, accounting for interactions between the CNTY and the typical heterogeneous, anisotropic surrounding media, including the effects induced by the curing process of the composite matrix. This study reports experimental results on the mechanical response of laminated composite materials under quasi-static and vibration loading monitored using integrated CNTY sensors. A combination of CNTY sensor configurations and experimental setups were used to monitor the deformation and strains among the various layers of the laminated composites. As the laminated composites were mechanically loaded under quasi-static four-point bending, the CNTY sensors captured instantaneously the deformation as demonstrated by the change in their electrical resistance. Also, as the laminated composites were subjected to sinusoidal loading at specific frequencies, the integrated CNTY sensors were able to capture the loading cycles exactly including durations and peaks. Integrated sensing using CNTYs may offer a highly adaptive, practical, and sensitive structural monitoring method for a variety of applications.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.The combined effects of hygrothermal conditions and material characteristics on the buckling response of laminated composite plates are numerically studied in this paper. As the physical mechanisms determining the environmental and operational conditions are very complex, the temperature and moisture variations throughout a structure can hardly be controlled in many cases of industrial interest. Also, inherent material variability are present in the structure domain due to manufacturing processes, specially involving composite materials. As a consequence, the characterization of the environmental and material influences as random quantities is more appropriate. Motivated by situations found in aerospace structural engineering, this paper aims to investigate the influence of space-dependent random hygrothermal conditions, geometry and material properties on the critical buckling loads of composite laminate plates. The main contributions lie in the consideration of simultaneous random quantities affecting the structural stability and combined influences of the environmental effects both on the degradation of material properties and the occurrence of stresses induced by hygrothermal changes. Under the hypotheses of the Classical Lamination Theory, a finite element model is employed to perform buckling analysis considering hygrothermal and mechanical loadings, where the degradation of material properties is predicted using a micromechanical approach. The space-dependent fluctuations of temperature, fiber-direction angle, ply thickness, and fiber volume fraction are discretized as stationary two-dimensional random fields by the Karhunen-Loève expansion (KLE), considering non-Gaussian marginal distribution functions, where the simulation are conducted using a methodology based on the Iterative Translation Approximation Method (ITAM). Monte Carlo Simulation, combined with the Latin Hypercube Sampling, is used to generate sampling-based statistics for the critical buckling load considering different values of standard deviations and correlation lengths associated to the random fields. From the simulation scenarios analyzed, the necessity of accounting for random environmental and material uncertainties in the analysis and design of reliable and robust composite structures is highlighted.

© Published under licence by IOP Publishing Ltd.The study introduced in this work is motivated by the prospect of using a hanging chain as an Acoustic Black Hole (ABH) for passive vibration control. An ABH is effectively a waveguide in which a wave slows progressively as it propagates away from the source enabling it to be extinguished with modest damping. The effect can be achieved by engineering inhomogeneity into a structure's geometry or material, the most common realisation being a beam of tapered thickness. This paper proposes an alternative realisation, that of a chain hanging under its own weight. Such a system has a wave speed that naturally decreases to zero, owing to its linear variation in tension, thus overcoming the challenges of constructing precisely shaped beams with vanishingly thin tips. The study of transverse vibration of hanging chains is a classical problem in structural dynamics. The motion of the chain can be described in terms of Bessel or Hankel functions, which are needed to account for the variation in tension along the chain. In this work, the hanging chain problem is revisited from a wave propagation perspective. An expression is derived for the amplitude of the waves in an infinite chain due a point excitation. From which, the spatial behaviour and the receptances of the waves are evaluated, revealing differing characteristics of upward and downward propagating waves. Some experimental results are presented to support the theoretical analysis.

© 2024Conductive inks are essential components in electronics as they enable the printing of electronic circuits and components on diverse surfaces. Furthermore, they can be easily tailored to enhance chemical bonding with specific targets in sensing devices. This technology plays a crucial role in the development of both rigid and wearable sensors. Conductive inks for printed electronics and sensor devices should possess several key characteristics, including high conductivity, flexibility, affordability, and compatibility with various substrates. However, conventional conductive inks based on metal nanoparticles tend to be expensive and lack flexibility. This study aims to produce a conductive ink comprised of carbon-black-derived flash graphene (CBFG) and poly(o-methoxy aniline) (POMA), which can be applied to electronic devices. The structures and morphology of both precursors were assessed, and the electrical conductivity of ink coatings containing CBFG, POMA, and a combination of both was investigated. The effect of each component's concentration on the ink's electrical conductivity (EC) was investigated using a 23 factorial design of experiment. In conclusion, the most conductive film presented an EC of approximately 0.768 S m−1 when the concentrations of graphene, POMA, and binder were 40.0, 2.0, and 4.0 mg L−1, respectively. While further research is needed to explore the flexibility and adhesion properties of the ink on different substrates, our solvent and organic-based conductive ink offer environmental benefits and boost sensor performance.

© 2024In this work we demonstrate the achievement of significative improvements in the structural and morphological quality of wurtzite GaN films (approximately 250 nm thick) by introducing an initial growth step involving an AlGaN buffer layer on p-type Si (100) substrates through a continuous reactive sputtering process. We investigated the influence of using single and multiple AlxGa1-xN buffer layers with varying Al content (x ranging from 0.07 to 0.37) and different thicknesses (from 166 nm to 1 µm). The obtained samples underwent characterization through X-ray diffraction and scanning electron microscopy. The results reveal a slight increase in the c-axis preferred growth direction and grain sizes even with a single and thin (250 nm) Al0.07Ga0.93N buffer layer. Conversely, the use of a single Al0.37Ga0.63N buffer layer led to significant morphological changes and a remarkable improvement in the c-axis preferred orientation. The most favorable outcomes were observed with the implementation of a triple AlGaN buffer layer, featuring decreasing Al content from the substrate, indicating the attainment of a high-quality GaN top layer comparable to epitaxial GaN.

© 2024, Escola de Minas. All rights reserved.A Hollow Cathode Plasma Enhanced Chemical Vapor Deposition (HC-PECVD) reactor was used to deposit silver doped Diamond-Like Carbon (Ag-DLC) films on Ti6Al4V alloy employing two methodologies: i) producing a silicon interlayer, using tetramethylsilane (TMS) as silicon precursor, varying the argon flow of the hollow cathode; and ii) carbonitriding the substrate. Profilometry, Raman, and Secondary Ion Mass Spectrometry (SIMS), as well as nanohardness, micro-scratch, scratch, and VDI 3198 indentation tests were used to evaluate the characteristics of the films and their adhesion on the substrates. The results demonstrated that the argon flow can be used for tuning the Ag-DLC film’s hardness, toughness, and adherence on silicon interlayers. The carbonitriding process, in turn, provided an improvement in the film toughness compared with non-carbonitrided samples. Considering the lower cost and easier handling of N2 compared to the silicon precursors commonly available (TMS, HDMSO, SiH4, etc.), the carbonitriding process proved more appropriate to improve the adhesion of the Ag-DLC films on the Ti6Al4V alloy.

© The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2024.The root pass represents a challenge for welders. Being the first pass of the joint, it requires full penetration and is more prone to metallurgical defects. There needs to be a balance between the forces acting on the molten pool to avoid incomplete penetration or burnthrough. Additionally, the hardness in the heat affected zone (HAZ) should not exceed 350 HV, beyond which there is susceptibility to cold cracking. When different thicknesses are present in the joints, it is often thought that greater thicknesses require higher welding energy (the ratio between power and welding speed). This has also been verified in the literature. The present work aims to test if it be possible to weld the root pass of four plates of different thicknesses (7 mm, 10 mm, 12.7 mm, and 25.4 mm) considering a similar welding energy. This would make the parameterization robust, as the welder would not need to change the welding energy to perform the process under different conditions. An experimental evaluation was conducted on shipbuilding steel ASTM A131 DH36 using the GMAW process, evaluating both the geometric characteristics of the weld bead and the microstructure at different thicknesses. Cooling rates were predicted based on an in-house finite volume method (FVM) computational code. The results indicated that although all welds met the main requirement of full penetration, the metallurgical requirement of a maximum hardness of 350 HV in the HAZ was only achieved at thicknesses of 7 mm and 10 mm. This occurred because, in greater thicknesses (12.7 mm and 25.4 mm), the cooling rate was elevated due to the thickness itself and the use of a higher feed rate. Consequently, in the coarse grain heat affected zone (CGHAZ), there was a shift from the ferritic field to the bainitic field. To meet the requirements, it is advisable to adjust parameters, such as increasing weld energy or applying preheat treatment. Another alternative involves planning subsequent passes to induce a tempering effect on the root. In summary, for geometrical purposes, a constant energy can be used, whereas metallurgical objectives might necessitate greater energy input with increasing thickness.

© 2024 by the authors.This research develops an innovative framework for accelerating Conjugate Heat Transfer (CHT) simulations within squared heated cavities through the application of Graphics Processing Units (GPUs). Although leveraging GPUs for computational speed improvements is well recognized, this study distinguishes itself by formulating a tailored optimization strategy utilizing the CUDA-C programming language. This approach is specifically designed to tackle the inherent challenges of modeling squared cavity configurations in thermal simulations. Comparative performance evaluations reveal that our GPU-accelerated framework reduces computation times by up to 99.7% relative to traditional mono-core CPU processing. More importantly, it demonstrates an increase in accuracy in heat transfer predictions compared to existing CPU-based models. These results highlight not only the technical feasibility but also the substantial enhancements in simulation efficiency and accuracy, which are crucial for critical engineering applications such as aerospace component design, electronic device cooling, and energy system optimization. By advancing GPU computational techniques, this work contributes significantly to the field of thermal management, offering a potential for broader application and paving the way for more efficient, sustainable engineering solutions.

© 2024 by the authors.Thermally characterizing high-thermal conductivity materials is challenging, especially considering high temperatures. However, the modeling of heat transfer processes requires specific material information. The present study addresses an inverse approach to estimate the thermal conductivity of SAE 1020 relative to temperature during an autogenous LASER Beam Welding (LBW) experiment. The temperature profile during LBW is computed with the aid of an in-house CUDA-C algorithm. Here, the governing three-dimensional heat diffusion equation is discretized through the Finite Volume Method (FVM) and solved using the Successive Over-Relaxation (SOR) parallelized iterative solver. With temperature information, one may employ a minimization procedure to assess thermal properties or process parameters. In this work, the Quadrilateral Optimization Method (QOM) is applied to perform estimations because it allows for the simultaneous optimization of variables with no quantity restriction and renders the assessment of parameters in unsteady states valid, thereby preventing the requirement for steady-state experiments. We extended QOM’s prior applicability to account for more parameters concurrently. In Case I, the optimization of the three parameters that compose the second-degree polynomial function model of thermal conductivity is performed. In Case II, the heat distribution model’s gross heat rate (Ω) is also estimated in addition to the previous parameters. Ω [W] quantifies the power the sample receives and is related to the process’s efficiency. The method’s suitability for estimating the parameters was confirmed by investigating the reduced sensitivity coefficients, while the method’s stability was corroborated by performing the estimates with noisy data. There is a good agreement between the reference and estimated values. Hence, this study introduces a proper methodology for estimating a temperature-dependent thermal property and an LBW parameter. As the performance of the present algorithm is increased using parallel computation, a pondered solution between estimation reliability and computational cost is achieved.

© 2024 by the authors.The maximum number of parallel threads in traditional CFD solutions is limited by the Central Processing Unit (CPU) capacity, which is lower than the capabilities of a modern Graphics Processing Unit (GPU). In this context, the GPU allows for simultaneous processing of several parallel threads with double-precision floating-point formatting. The present study was focused on evaluating the advantages and drawbacks of implementing LASER Beam Welding (LBW) simulations using the CUDA platform. The performance of the developed code was compared to that of three top-rated commercial codes executed on the CPU. The unsteady three-dimensional heat conduction Partial Differential Equation (PDE) was discretized in space and time using the Finite Volume Method (FVM). The Volumetric Thermal Capacitor (VTC) approach was employed to model the melting-solidification. The GPU solutions were computed using a CUDA-C language in-house code, running on a Gigabyte Nvidia GeForce RTX™ 3090 video card and an MSI 4090 video card (both made in Hsinchu, Taiwan), each with 24 GB of memory. The commercial solutions were executed on an Intel® Core™ i9-12900KF CPU (made in Hillsboro, Oregon, United States of America) with a 3.6 GHz base clock and 16 cores. The results demonstrated that GPU and CPU processing achieve similar precision, but the GPU solution exhibited significantly faster speeds and greater power efficiency, resulting in speed-ups ranging from 75.6 to 1351.2 times compared to the CPU solutions. The in-house code also demonstrated optimized memory usage, with an average of 3.86 times less RAM utilization. Therefore, adopting parallelized algorithms run on GPU can lead to reduced CFD computational costs compared to traditional codes while maintaining high accuracy.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.Conjugate heat transfer plays a crucial role in numerous engineering applications, such as thermal management of electronic devices, aerospace heat shields, and energy systems. This paper explores the utilization of Graphics Processing Units (GPUs) and the CUDA-C programming language for solving conjugate heat transfer problems. Three distinct heat transfer scenarios are investigated: the Lid-Driven cavity, squared cavity with natural convection, and squared cavity with a solid square embedded in the center. These problems are solved using numerical methods and parallelized using GPU computing techniques to enhance computational efficiency and reduce simulation time. The Lid-Driven cavity problem involves the flow of a fluid within a square enclosure, where one side is subjected to a constant velocity boundary condition. In the squared cavity with natural convection, the study focuses on heat transfer phenomena occurring due to density-driven fluid motion. The buoyancy effects induce convective currents within the cavity, influencing the temperature distribution. The squared cavity with a solid square in the center represents a more complex conjugate heat transfer problem. The presence of the solid square influences the flow patterns and temperature distribution within the cavity. Through the utilization of GPUs and CUDA-C programming, the computational efficiency of solving conjugate heat transfer problems is greatly enhanced. The parallel processing capabilities of GPUs enable accelerated simulations, reducing the time required for solving these complex problems. The study demonstrated that the proposed algorithm achieved up to 99.7% reduction in simulation time for the laminar lid-driven cavity problem. The results obtained from the simulations provide valuable insights into the heat transfer characteristics, facilitating the optimization of thermal management systems and the design of more efficient heat exchangers. Overall, this study demonstrates the effectiveness of GPU computing in tackling conjugate heat transfer problems and its potential for advancing the field of thermal sciences.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.The recent advancements in computer hardware opened new doors to the modeling and simulation of intensive Computational Fluid Dynamics (CFD) problems. The advent of modern Graphics Processing Units (GPUs) made parallel computing easier by allowing cards to run multiple kernels in several parallel threads with double-precision. However, traditional CFD codes still lack hardware usage optimization due to a low threads scalability computing methodology. Hence, a computational performance investigation between codes run on GPU and Central Processing Unit (CPU) is presented in this work. The analysis was focused on the three-dimensional simulation of a Laser Beam Welding (LBW) process with a moving heat source and non-linear thermal properties. The solutions were developed by applying the Finite Volume Method (FVM) to solve the transient heat conduction Partial Differential Equation (PDE). The phase change was accounted through the enthalpy method. A time and space-dependent Gaussian conical volumetric profile was used to model the heat source. The GPU solutions were computed by a CUDA-C in-house code running on a Nvidia Geforce RTX™ 3090 and RTX™ 4090 video cards, both with 24 GB of memory. Three equivalent solutions were produced by top-rated commercial codes. All codes were run on an Intel® Core™ I9 12900KF CPU with 3.6 GHz base clock and 16 cores. The results evidenced that GPU and CPU processing are similarly precise but GPUs can achieve far faster and more power efficient CFD solutions. The GPU code demonstrated better memory optimization when simulating LBW.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.In the present study, the Quadrilateral Optimization Method (QOM) is applied for parameter estimation in an inverse heat transfer problem. A numerical LASER Beam Welding (LBW) experiment of SAE 1020 is the baseline for the estimations. The temperature-dependent thermal conductivity of the steel is assessed. The algorithm accounts for the conductivity as a second-degree polynomial function of temperature. The three parameters of the function are simultaneously assessed. The method regularizes the objective function through Future Time Regularization (FTR) to account for the temporal analysis. Hence, the effect of using different numbers of time steps was analyzed. The most accurate results were found when considering 60 points. Thus, this configuration was set to expand the algorithm to assess the gross heat rate provided by the LASER along with the thermal conductivity function. The results are sensitive enough to represent reliable assessments. Considering the reference and estimated values, the simulated temperatures show good agreement. The present algorithm requires low computational cost due to a GPU’s parallel computation.

© 2024 Begell House Inc.. All rights reserved.This study introduces NEMESYS, a novel algorithm designed to exploit the parallel processing capabilities of Graphics Processing Units (GPUs) to significantly enhance computational efficiency in fluid dynamics simulations. NEMESYS integrates the Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε turbulence model, and its efficacy is validated through simulations of two classical flow scenarios: laminar flow around a cylinder, exhibiting von Kármán vortex shedding, and turbulent flow over a backward-facing step. The algorithm's performance is critically assessed against established benchmarks from scientific literature and leading commercial Computational Fluid Dynamics (CFD) software. Key performance metrics include the Strouhal number for the cylinder flow and reattachment length for the backward-facing step flow. Results demonstrate remarkable accuracy and reliability of NEMESYS, with a notable reduction in computation time – up to 99.5% faster than traditional CPU-based software. This substantial reduction in computational effort presents significant cost savings and opens new avenues for real-time analysis and accelerated design processes. The implications of this advancement are far-reaching, offering transformative potential for various engineering domains, such as automotive, civil, and environmental engineering, thereby redefining approaches to fluid dynamics analysis and design.

© 2024 Begell House Inc.. All rights reserved.In the field of Computational Fluid Dynamics (CFD), solving conjugate heat transfer problems involving natural convection remains a computationally demanding endeavor. This study presents the NEMESYS algorithm, specifically optimized for Graphics Processing Units (GPUs), with an application focused on natural convection in a square cavity that incorporates a centrally situated solid block. This complex configuration necessitates the concurrent resolution of the Navier-Stokes equations governing fluid flow and the energy equation governing heat conduction in both fluid and solid phases. Through the efficient utilization of GPU-based parallel processing, the NEMESYS algorithm managed to markedly reduce the computational burden. A quantifiable 99.5% time reduction was recorded when compared to equivalent Central Processing Unit (CPU)-based simulations, thereby manifesting a significant leap in computational efficiency. To authenticate the algorithm's credibility, an exhaustive validation process was undertaken. The simulation results were cross-verified against established benchmarks from academic literature as well as outputs from widely used commercial CFD software packages. This validation revealed strong agreement in critical parameters such as fluid velocity and temperature distributions within the fluid cavity, as well as heat conduction characteristics within the solid block. In summary, the NEMESYS algorithm emerges as a reliable, efficient computational framework for tackling the intricacies of natural convection problems involving conjugate heat transfer and holds potential for broader adaptability in high-fidelity CFD simulations.

© 2023 Taylor & Francis Group, LLC.Modern engineering applications use processes that submit materials to high-temperature gradients. However, the traditional experimentation methods applied to determine thermal properties often do not provide reliable data when working temperatures are up to extreme conditions. Hence, the present work demonstrates the use of an inverse heat conduction problem methodology for estimating the thermal properties of a laser beam welding (LBW) process. The applied technique is the quadrilateral optimization method (QOM), which consists of a multivariable estimation approach developed to calculate the function’s parameters. Additionally, the future time regularization scheme was implemented in the objective function to regularize the results. The applied numerical process solved the energy equation using the finite volume method implemented in an in-house CUDA-C language code. The software is a multi-thread application run in a graphics processing unit for enhanced computational time efficiency. A validation study compared the estimated results with LBW simulated data. The QOM estimates the parameters of a function representing the range of thermal conductivity values. The proposed method is expected to lower experimental costs for obtaining thermal properties at high temperatures by eliminating the need for sophisticated technical equipment and skilled labor required by traditional direct measurements.

© The Author(s), 2024.Runway overruns (ROs) are the result of an aircraft rolling beyond the end of a runway, which is one of the accident’s types that most frequently occurs on aviation. The risk of an RO arises from the synergistic effect among its precursors, such as unstable approaches, long touchdowns and inadequate use of deceleration devices. To analyse this complex socio-technical system, the current work proposes a customised functional resonance analysis method, called FRAM-FDM, as traditional techniques of risk and safety assessment do not identify the interactions and couplings between the various functional aspects of the system itself, especially regarding human and organisational components. Basically, FRAM-FDM is the coupling of a traditional FRAM with flight data monitoring (FDM) techniques, used here to quantify the variabilities of the flight crew performance while executing the required activity (i.e. the landing). In this proposal, these variabilities (i.e. the FRAM functions aspects) are aggregated by the addend of a logistic regression, resulting in a model to evaluate the flare operations and the brake application profile effect on the remaining distance to the end of the runway, used as a reference to classify the landing as acceptable or not. The present application of the FRAM-FDM assesses the operational risk of a sample fleet in overrunning the runway during landing, highlighting the brake pedal application profile as the most relevant contributor. The model improves the knowledge about the system behaviour, being useful to direct flight crew training.

© 2024 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.This paper proposes a framework for aircraft fault diagnosis based on the offline analysis of flight data. It overcomes the limitations of current data-driven approaches by combining steps based on both real data, obtained from aircraft flight data records, and simulated data, generated from aircraft models. The framework explores unsupervised and supervised methods, resulting in a proactive approach to flight safety and speeding the learning of fault cases. The influence of both temporal data representation and sensor selection on fault diagnosis performance is analyzed. The framework is organized into four phases (initial, training, operation, and improvement) that cover the aircraft system lifecycle. We used the hierarchical clustering algorithm in the unsupervised part and an ensemble of three algorithms (k-nearest neighbors, decision trees, and neural networks) in the supervised one. The framework is evaluated using an aircraft electrohydraulic actuating system as the case study, for which we obtained a balanced accuracy of 96% in the operation phase and of 90.4% in the improvement phase. The contribution of the framework is also accessed through a comparison with results obtained using only supervised methods. It confirms that the combination of supervised and unsupervised methods improves the performance of the fault diagnosis system.

© 2024 IEEE.High fidelity flight simulators use motion platforms to reproduce the feeling of motion from a real flight. While most of the published works for both aircraft and vehicle simulators are related to parallel motion platforms, this work approaches the problem of designing the motion cueing algorithm of a flight simulator based on a serial manipulator. The simulator presents a large cockpit with an embedded visual system and dimensions that resemble those of an aircraft flight deck. Motion cueing in this context should be able to minimize false cues while ensuring safe operation, coping not only with the dynamic and kinematic constraints of the robot but also avoiding crash events that might happen between the cockpit and the serial arm. While there have been several contributions regarding classical filtering, tuning optimization, and model-based predictive control approaches to cope with constraints of parallel platforms, they result in the inefficient utilization of the robot workspace or even the inability to handle collisions of the cockpit with the robot. This work presents a novel motion cueing algorithm for a serial robotic flight simulator, which focuses on ensuring safety regarding the physical boundaries of the cockpit while enhancing motion fidelity. The approach is based on a hybrid model-based predictor that uses a neural network to infer workspace collisions in real-time (including crash events of the cockpit with the robotic arm), releasing a non-linear deterministic control action that acts as a feedforward reference governor. Simulation and experimental results evince improved workspace usage while ensuring safe operation.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.This paper conducts a systematic quantitative literature review exploring the interplay between human factors and artificial intelligence (AI) in Manned-Unmanned Teaming (MUM-T) contexts. With AI’s rapid advancement and its growing role in military operations, especially in UAV management, a deeper understanding of how human cognitive capabilities intersect with AI is crucial. This review meticulously evaluates the existing body of literature, following a methodical process of gathering information, building a database, and generating a thorough analysis. The results of this review are organized into principal thematic areas, including levels of autonomy, the dynamics of trust in human-machine interactions, cognitive workload management, experimental practices, and analysis of human factors. The findings underscore the intricacies of integrating AI with human operators in MUM-T scenarios, revealing both challenges and opportunities. This comprehensive literature overview aims not only to synthesize current knowledge but also to guide future research and development in the domain, underlining the need for strategies that effectively marry AI capabilities with human expertise in complex military operations.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.Robotics is a constantly evolving field that benefits from the use of tools powerful tools for robot development and simulation. Two of these tools, widely used ROS (Robot Operating System) and CoppeliaSim (formerly known as V-REP). ROS is an open-source framework widely used in the robotics community. On the other hand, CoppeliaSim is a simulation platform for powerful and versatile 3D robots. In this paper, we distributed an F16 simulation using ROS to create tasks, combining flight visualization by Flight Gear and collision analysis of a robotic flight simulator using CoppeliaSim.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.In aviation safety and performance play a pivotal role, and a critical theory part is fault detection, which can be used in subsystems that are important in ensuring the reliability of aircraft systems. This research delves into the implementation and testing of an architecture for fault detection using parity space methodology, specifically tailored to handle different maneuvers during the flight of an aircraft. The emphasis on maneuver-specific techniques aims to enhance fault detection’s overall robustness and accuracy in dynamic flight conditions. This work is intended to study two different forms of implementation for detecting faults in the actuator system of an aircraft, they will be tested using two actuator models for the elevator in a simple maneuver during the flight.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.This study explores the cognitive and ergonomic aspects of military UAV operations, focusing on pilots' mental workload and interface usability using advanced eye-tracking technology. A total of 24 military pilots participated in 30-minute flight simulations, with their eye movements recorded by Tobii Pro Glasses 2 and analyzed using Tobii Pro Lab software. Pilots' subjective perceptions of workload and interface usability were assessed through NASA-TLX and SUS questionnaires. Statistical analyses, including Pearson correlation, ANOVA, and linear regression, were conducted to examine the relationships between eye-tracking metrics (fixation duration, saccade amplitude, blink rate, and pupil dilation) and subjective assessments. The findings indicate that experienced pilots rated UAV interfaces as more usable, and higher mental workload, indicated by NASA-TLX scores, was strongly correlated with increased pupil dilation and blink rate. These results demonstrate the value of integrating eye-tracking technology with subjective assessments to achieve a comprehensive understanding of UAV operator interactions. The insights gained can inform the design of more intuitive and efficient UAV interfaces and training programs, enhancing operational safety and efficiency. This study contributes significantly to military aviation training and interface design, emphasizing the necessity of incorporating technological advancements with human factors to optimize UAV operations.

© 2024This paper presents a state of the art on port-Hamiltonian formulations for the modeling and numerical simulation of open fluid systems. This literature review, with the help of more than one hundred classified references, highlights the main features, the positioning with respect to seminal works from the literature on this topic, and the advantages provided by such a framework. A focus is given on the shallow water equations and the incompressible Navier–Stokes equations in 2D, including numerical simulation results. It is also shown how it opens very stimulating and promising research lines towards thermodynamically consistent modeling and structure-preserving numerical methods for the simulation of complex fluid systems in interaction with their environment.

Copyright © 2024 The Authors.The complexity of highly flexible structures restricts their use in real-time simulations. To address this challenge, we investigate the use of Hamiltonian neural networks (HNNs) as an alternative method for modeling a highly flexible cantilever beam. We derived the reference structural model using a lumped-mass rigid multibody method considering the Hamiltonian formalism and used it to generate a dataset consisting of generalized coordinates and momenta as inputs and their respective time derivatives as outputs. The trained neural networks are used as surrogate models to simulate the cantilever beam under free and forced conditions. Preliminary findings indicate that HNNs create accurate and efficient surrogate models whilst learning conservation laws. For forced-response simulations, our approach requires analytical calculation of external forces, offsetting the computational efficiency gains of our surrogate models. The outcomes of this study give initial perspectives and limitations of the use of surrogate models based on HNNs as a means to efficient simulations of highly flexible structures.

Copyright © 2024 The Authors.This paper contributes to the application of port-Hamiltonian systems (pHs) theory in the context of fixed-wing airplanes, an area challenged by the difficulty of introducing aerodynamics in this framework. Expanding on recent initiatives that applied pHs theory to fixed-wing airplane dynamics - a move that simplified thrust and aerodynamics - our study introduces a comprehensive longitudinal dynamics formulation. This approach not only clarifies these earlier models by aligning more closely with traditional airplane dynamics equations but also integrates physical parameters from an A300 airplane model. By addressing and enhancing the thrust and aerodynamic representations, our formulation achieves a more accurate depiction of airplane dynamics. This work marks a step forward in the ongoing efforts to adapt pHs theory for aerospace engineering, laying the groundwork for more effective modeling and control strategies in this field.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Most performance data reduction methods rely on the availability of a flight thrust deck. Nevertheless, for many reasons, such as industrial intellectual property, this information is not always available for the aircraft end user, or has prohibitive costs. For that reason, the ability to estimate an engine flight thrust deck based on flight data may be of special interest for flight test organizations or flight test schools. Thus, the objective of this work is to demonstrate a flight test method that enables the estimation of a reliable engine deck, using limited flight test instrumentation. The proposed method uses the specific excess power to estimate the thrust and drag balance. By combining level flight accelerations at constant altitudes and climb/descents at constant Mach numbers, using different thrust settings, it was possible to estimate the engine thrust for a combination of engine rotation speeds, altitudes, and airspeed. Using the method, it was also possible to estimate the drag polar at different Mach numbers.

© 2024 International Forum on Aeroelasticity and Structural Dynamics, IFASD 2024. All rights reserved.The analysis of aircraft loads during flight maneuvers plays a pivotal role in ensuring structural integrity, safety, design of lighter structures and more fuel-efficient vehicles. This study focuses on a comparative analysis of internal load diagrams and flight parameters time histories for a flexible aircraft and its rigid-body counterpart, emphasizing the impact of structural flexibility on flight dynamics and loads during flight maneuvers. The research employs a dynamically-coupled formulation for the flexible model, considering small deformations and inertially coupled equations of motion. The aerodynamic loads are calculated with a quasi-steady VLM model, and the structural dynamics is represented by a linear FEM model. The rigid-body model is obtained by neglecting structural flexibility, setting the number of elastic modes to zero. To calculate the internal loads, the force summation method is employed. Three maneuvers from CS-25 specifications are simulated: the symmetrical unchecked and checked maneuvers, and the roll maneuver. For the unchecked and roll maneuvers, the flexible model exhibits a slightly slower response and reduced wing and horizontal tail loads compared to the rigid model. In the checked maneuver, the flexible model displays nuanced differences in flight dynamics and horizontal tail loads, computing higher absolute TMY values, and higher SLZ and BMX loads at the instant of maximum positive FZTH, while the rigid-body model presented higher absolute values of SLZ and BMX. Regardless of the obtained variations, the study emphasizes the importance of considering structural flexibility in analyzing flight maneuver loads and the need for more precise and efficient methods to address the evolving landscape of aircraft design.

© 2024 International Forum on Aeroelasticity and Structural Dynamics, IFASD 2024. All rights reserved.Flexible structures are increasingly prevalent in the commercial aviation industry, and the use of highly flexible structures is a prominent trend for the future. When analyzing those structures, it is crucial to consider geometric nonlinearities caused by large displacements. This means that the modeling of the structures must incorporate nonlinear structural models, which can lead to a reasonable increase in computational costs. To tackle this challenge, a framework has been developed for static and dynamic analyses of highly flexible structures. It is based on a linear structural model, utilizing the Rayleigh-Ritz method, coupled with multibody dynamics. The geometric nonlinearities are modeled through rigid connections between multiple flexible bodies that form the final structure. Two different approaches have been used for the multibody dynamics. The former considers all degrees of freedom of each body and solves only the kinematics of the constraint to maintain the connections between the bodies, which resulted in an augmented system with Lagrange multipliers that can be used to reconstruct forces and moments of constraint. The latter utilizes only the independent degrees of freedom whilst reconstructing the dependent ones through the equations that define the constraints between the bodies, directly solving the constraints. The results obtained show that proposed framework accurately describes the dynamics of highly flexible structures and can be used to simulate structures with various types of connections, showcasing its versatility for other applications like simulations of morphing structures such as wings with folding wingtips.

© 2024 International Forum on Aeroelasticity and Structural Dynamics, IFASD 2024. All rights reserved.The necessity to mitigate pollutant emissions highlights the importance of research into flexible aircraft. Identifying models that accurately represent these aircraft is essential for the validation of early-stage design models and control design. This study focuses on performing a parametric system identification in the time domain for aircraft with varying levels of flexibility. The approach employs a simplified longitudinal stability and control model for short-period dynamics, rooted in the Quad-M methodology (Maneuver, Measurements, Model, and Method). The system identification technique used is the output error method, applied to a flexible model aircraft in three different flexibility configurations. Data were collected through nonlinear simulation of the flexible aircraft. Comparison of identification results across the different flexible configurations indicates an improvement in parametric values by incorporating elastic effects into the identification models. The study also explores the feasibility of various sensors to more closely simulate flight test procedures. Identifications are analyzed by comparing deflection measurements and accelerometers as observational variables, with acceleration measurements providing more accurate parameter estimations. Future work should extend the analysis presented to system identification using flight test data.

© 2024 International Forum on Aeroelasticity and Structural Dynamics, IFASD 2024. All rights reserved.The renaissance of neural networks in the scientific community in recent years has brought new perspectives for improving the computational efficiency of traditional modeling techniques. Hamiltonian neural networks leverage the energy-preserving properties of the Hamiltonian formalism to provide surrogate models with increased interpretability compared to conventional feed-forward models. In this study, we employ a lumped-mass multibody method to derive the equations of motion of two highly flexible structures. We perform a model order reduction via modal decomposition while preserving the nonlinearities with the use of exact kinematic relations. After validating full- and reduced-order models, we use them to produce datasets and train the neural networks, which serve as ready-to-use surrogate models. Preliminary findings show that the surrogate models based on neural networks can significantly reduce the time necessary to simulate the free response of the structures. Furthermore, we demonstrate that surrogate models based on Hamiltonian neural networks have energy-preserving capabilities, maintaining accuracy levels even for long simulations. Due to their architecture, when external loads are considered, the surrogate models require the analytical calculation of the generalized forces, jeopardizing the efficiency gains obtained by our approach. We also present initial findings on the use of neural networks for faster aerodynamic models for flexible aircraft, particularly as surrogate models for the vortex-lattice method. By using a neural network as the aerodynamic surrogate model in a specific flexible aircraft simulation framework, the computational costs were reduced by a factor of 100 on average. The outcomes of this study demonstrate that surrogate models based on neural networks can soon become an efficient and reliable alternative for modeling arbitrarily flexible aircraft, provided the current limitations are addressed.

Copyright © 2024 Techno-Press, Ltd.Curved hexahedral finite elements based on the hybrid-mixed stress formulation are proposed for structural dynamic analysis of three-dimensional solids. The stress and displacement in the domain of an element and the displacement on its boundary are simultaneously and independently approximated using sets of complete and linearly independent non-nodal Legendre polynomials. The element geometry is given in terms of its corner and mid-edge points using the same interpolation functions of the traditional isoparametric 20-node brick element. Symmetric, highly sparse and well conditioned solving systems are obtained. Numerical tests are carried out using h- and p-refinements to assess the behavior of these new hexahedrons.

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.An evaluation of the commercial transport aircraft developed over the past decades evidences an increasing trend toward the use of high aspect-ratio wings. This trend is justified by the well-known effect of slender wings in reducing fuel consumption, leading to lower operational costs and a milder environmental impact. There are many studies about the effects of geometric nonlinearities on aeroelastic behavior of very flexible wings in symmetrical maneuvers. However, geometric nonlinearities may also significantly affect the aeroelastic behavior of the wing under non-symmetrical conditions, especially when ailerons are deflected. Within this context, this work presents a static fluid–structure interaction approach to evaluate the rolling characteristics of very flexible wings. First, a modified version of the very flexible Pazy Wing from Aeroelastic Prediction Workshop (AEPW-3) is proposed, now equipped with ailerons. Next, a fluid–structure interaction tool that couples a full potential aerodynamic solver with an implicit nonlinear structural solver is presented to allow simulations of wings with deflected ailerons. The presented method is applied to the modified Pazy wing considering multiple linear and nonlinear structural analyses, for different aileron deflection angles. The results show that when geometric nonlinearity effects are considered, the aileron effectiveness tends to decrease as the structural flexibility increases. On the other hand, if geometric nonlinearities are neglected, the aileron effectiveness falsely enhances as the wing flexibility rises.

© 2024 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.This work presents a decade of outcomes of Static Aeroelasticity of high aspect ratio wings for the Structures technology. There are considerable improvements in Aeroelasticity field by incorporating structural geometric nonlinearity to understand high span wing behavior. However, there is a lack of investigation on how the Aeroelasticity outcomes influences Structures technology, their interface information, and methodologies. Thus, this paper presents the high-fidelity methodology E2-FSI&SS as means to expose the chain of effects culminating in a different structural sizing concerning stress and buckling at limit static load. Here high flexibility is considered by adding structural geometric nonlinearity in the static aeroelasticity, to obtain follower loads, and in the sizing of the structure itself. The method is applied to a very flexible wing of a transport aircraft from 50 to 150 passengers. The differences found by considering and not considering the static aeroelasticity of high flexibility wings in limit flight loads are 14% in internal load, up to 82% in stress and 30% in buckling load factor.

© 2024 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.In this paper, collaborative aeroelastic analyses of the Pazy Wing are presented, which support the activities of the Large Deflection Working Group, a sub-group of the 3rd Aeroelastic Prediction Workshop (AePW3). The Pazy Wing is a benchmark for the investigation of nonlinear aeroelastic effects at very large structural deflections. Tip deformations on the order of 50% semi-span were measured in wind tunnel tests at the Technion - Israel Institute of Technology. This feature renders the model highly attractive for the validation of numerical aeroelastic methods for geometrically nonlinear, large deflection analyses. A distinguishing feature of the Pazy Wing is that its flutter speed is a function of the static deformation, and capturing this effect requires a nonlinear aeroelastic framework which allows for stability (flutter) analyses about steady states of large deformations. In particular, the flutter characteristics of the model are dominated by a hump mode which develops due to the coupling of the first torsion and the second out-of-plane bending mode; this hump mode moves towards lower airspeeds as the steady structural deformation increases. Different nonlinear aeroelastic solvers were applied by the authors to obtain static coupling and flutter results for a series of airspeeds and angles of attack. The results reveal that the decisive nonlinear effects were captured very well by the applied methods and computational tools.

© 2024 by the American Institute of Aeronautics and Astronautics, Inc.This study investigates the nonlinear aeroelastic stability of the Pazy wing, a benchmark for theoretical aeroelastic research analysis within the Third Aeroelastic Prediction Workshop (AEPW 3 - NASA). Many institutions were challenged to predict the static deflections and flutter behavior in this case of a highly flexible wing subjected to structural geometric nonlinearity with flutter onset and offset along the wind-tunnel test. This paper presents the effort of the ITA-Embraer team in creating a methodology for matched flutter solution. The traditional flutter analysis is applied in a new nonlinear fluid-structure framework to explicitly account for solely the structural deflection with geometric nonlinearity. First the theoretical vibration modes are presented in comparison to test, which was within 3.5% difference. Then, the theoretical flutter speed are compared to experimental results, within 3.3% difference for onset and 2.8% difference for offset. When comparing theoretical undeformed condition to nonlinearly deformed condition there was 26 to 41% difference in flutter speed depending on the angle of attack. The results indicate that the matched solution approach is effective in capturing the flutter velocity with good accuracy being a simplified approach for capturing the main physics behind the problem.

© 2024 IOP Publishing Ltd.Methane reforming is gaining attention because of its potential to be converted into energy-dense fuels or high-value chemicals. In addition to the production of syngas (H2+CO), the utilization of CO2 can help reduce greenhouse gases. Water steam is typically used to increase the output of H2. This study evaluated the potential of thermal plasma technology to produce clean hydrogen, carbon monoxide, and carbon black from methane by applying a thermodynamic equilibrium model. A comparative analysis of three cases of methane processing (pyrolysis, dry reforming, and steam reforming) is presented to provide a comprehensive understanding of the potential of thermal plasma technology for methane conversion.

© 2024 by the authors.This study explores the impact of non-stoichiometric aluminum oxide (AlxOy) coatings applied via thermal atomic layer deposition (ALD) on carbon fiber fabrics (CFFs), emphasizing volume per cycle, FESEM analyses, color transitions, and thermal stability enhancements. Using trimethylaluminum and water at 100 °C, AlxOy was deposited across a range of 1000 to 5000 ALD cycles, with film thicknesses extending up to 500 nm. This notable increase in the volume of material deposited per cycle was observed for the 3D CFFs, highlighting ALD’s capability to coat complex structures effectively. FESEM analyses revealed the morphological evolution of CFF surfaces post-coating, showing a transition from individual grains to a dense, continuous layer as ALD cycles increased. This morphological transformation led to significant color shifts from green to red to blue, attributed to structural coloration effects arising from variations in film thickness and surface morphology. Thermogravimetric analyses (TGA and dTG) indicated that the AlxOy coatings enhanced the thermal stability of CFFs, with a postponement in degradation onset observed in samples subjected to more ALD cycles. In essence, this research highlights the nuanced relationship between ALD processing parameters and their collective influence on both the aesthetic and functional properties of CFFs. This study illustrates ALD’s potential in customizing CFFs for applications requiring specific color and thermal resilience, balancing the discussion between the surface morphological changes and their implications for color and thermal behavior.

© 1973-2012 IEEE.In this work, we report the results from an optical emission spectroscopy experiment designed to investigate the molecular emissions from a plasma jet produced by a high velocity plasma spray (HVPS). By fitting the spectra, we were able to infer the rotational temperature of the electronic excited molecules OH (A2Σ +), CN (B2\Σ +), N2 (C2\Πu), and N 2+ (B2\Σ +u). We verified that rotational distributions were consistent with the local thermodynamic equilibrium hypothesis. However, the vibrational distribution of the excited species CN (B2Σ+) was overpopulated with respect to the expected equilibrium distribution. We proposed a model to describe this distribution, which provided good fittings. Lastly, we computed the energy balance equations of the sprayed particles with simplifying assumptions with the goal of getting some physical insight on the energy exchange dynamics between the plasma and the particles.

© 2024 Elsevier LtdThis study examined the impact of interfacial interactions on bilayer yttria-stabilized zirconia (YSZ) used in dental restorations. In-house bilayer structures of 3YSZ and 5YSZ composition underwent hydrothermal degradation to compare the properties of control and low-temperature degradation (LTD) treated groups. Biaxial flexural strength via piston-on-three-balls, staircase fatigue strength over 106 cycles at 15 Hz, phase characterization and quantification through XRD and Rietveld refinement, and fractography were conducted. Weibull analysis was employed to determine the Weibull modulus and characteristic strength. Results demonstrated an enhancement in the mechanical performance of 3YSZ composition after LTD treatment, whereas the mechanical properties of 5YSZ remained largely unaffected post-degradation. Fractographic analysis revealed that failure originated at the surface tensile location across all specimen groups. These findings offer insights into the mechanical behavior of bilayer zirconia structures and reinforce the significance of hydrothermal treatment in enhancing their performance, particularly in the case of 3Y compositions.

© 2024 John Wiley & Sons Ltd.The integration of bioglass with polymers in tissue engineering scaffolds holds promise for enhancing bone regeneration. This study explores the fabrication and characterization of composite scaffolds comprising polylactic acid (PLA)/polyethylene glycol (PEG) fibers incorporated with silicate-chlorinated bioglasses (45S5 and 58S). Electrospinning was utilized to produce the scaffolds, followed by physical–chemical and in vitro evaluations. Scanning electron microscopy (SEM) revealed uniform fiber formation, with bioglass incorporation observed in the composite groups. Bioglass incorporation led to a significant reduction in fiber diameter. Thermogravimetric analysis (TGA) estimated bioglass content, with 58S exhibiting the highest incorporation. Contact angle measurements indicated enhanced hydrophilicity in bioglass-containing groups. In vitro, bioactivity assessment in simulated body fluid (SBF) demonstrated apatite formation potential and the pH variance indicates a slightly alkaline to neutral condition. Cell culture studies revealed robust cellular adhesion and metabolic activity across all groups, with no cytotoxic effects observed. Overall, these findings suggest the potential of PLA/PEG bioglass composite scaffolds for bone tissue engineering applications.

© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.This study investigated the suitability of multiple bismuth sulfide (Bi2S3) samples for the photoreduction of Cr(VI) under simulated sunlight, aiming to elucidate the effect of different sulfide sources (thiourea, thioacetamide, sodium sulfide, potassium sulfide, and ammonium sulfide) on the final structural and photocatalytic properties of this semiconductor. The sulfides were produced through simple precipitation methods, without the necessity of complex methodologies or equipment. Additionally, the effect of thermal treatment on the properties of the Bi2S3 samples was also evaluated. The choice of the sulfide precursor imparted distinct characteristics onto the synthesized Bi2S3, such as distinct morphologies, specific surface areas (SSA), and crystalline structures. Notably, the efficiency of Cr(VI) photoreduction was found to be intricately linked to the adsorption capacity of Bi2S3. In this context, the calcination process emerged as a significant impediment, as it substantially diminished both the SSA and adsorption capacity of the materials. Among the sulfide sources investigated, Bi2S3 synthesized using K2S exhibited superior photoreduction efficiency, attributed primarily to its remarkable adsorption capacity and rod-like morphology. The photoreduction mechanism was determined to be carried out by the direct reaction between Cr(VI) and photogenerated electrons. Regarding operational parameters, initial concentration, pH and temperature had major effects on the photoreduction efficiency; high initial concentrations led to the saturation of the active sites and lower reaction rate constants, whereas lower pHs and higher temperatures favored the photoreduction process. As for the recycle tests of the best photocatalyst, it was discovered a significant efficiency loss between cycles, which was linked to the occlusion of active sites through the formation of chrome-based species on the surface of the photocatalyst. Graphical Abstract: (Figure presented.)

© 2024 Elsevier Ltd and Techna Group S.r.l.Two experimental ceramic systems, 3Y-TZP/5Y-PSZ (3Y/5Y) and 4Y-PSZ/5Y-PSZ (4Y/5Y), underwent analysis before (3Y/5Yi or 4Y/5Yi) and after hydrothermal aging (3Y/5Ya or 4Y/5Ya) to simulate low-temperature degradation (LTD). The samples were sintered and characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy, alongside nanoindentation tests to measure elastic modulus (Em) and hardness (H). Assessments were conducted on the external surfaces and at individual layers on cross-sectioned samples at predetermined regions of interest (ROIs). Degraded superficial regions were observed in the cross-sectional SEM images of the 3Y and 4Y zirconia layers after aging. XRD indicated a tetragonal→monoclinic phase transformation in the aged groups for both 3Y (66 % m-ZrO2) and 4Y (29 % m-ZrO2). Raman spectroscopy revealed monoclinic phase amounts of 86 % for 3Y and 62 % for 4Y in the degradation regions observed in the SEM micrographs. Monoclinic phase peaks were virtually no longer detected in either material beyond a depth of 15 μm. Hydrothermal aging significantly diminished the H and Em values for the 3Y and 4Y zirconia surfaces. For the analysis of different zirconia surfaces within the same subgroup, all pairwise comparisons showed statistically significant differences, except for the values of H of 3Y/5Yi and Em for 4Y/5Yi. Regarding the nanoindentation results of cross-sectioned samples, the aging protocol did not affect the H and Em values of the equivalent ROIs (layers), regardless of the bilayered system. However, significant differences in H values were observed among the ROIs (layers) within the same bilayered system. Despite surface changes, nanomechanical properties remained preserved below the surface and at the interfaces of bilayered materials after aging. Nanoscale H values varied among some layers and interfaces, whereas the Em values exhibited differences across certain surfaces.

© 2024 Elsevier Inc.Objectives: To assess the effects of different aging protocols on chemical, physical, and mechanical properties of an experimental ATZ composite compared to a zirconia. Methods: Disc-shaped specimens were obtained through uniaxial pressing of commercial powders (Tosoh), ATZ comprised of 80%ZrO2/20%Al2O3 (TZ-3YS20AB) and 3Y-TZP (3Y-SBE). The specimens of each material were divided into different groups according to the aging protocol: immediate, autoclave aging and hydrothermal reactor aging. The aging protocols were performed at 134 ºC for 20 h at 2.2 bar. Crystalline evaluations were performed using X-Ray Diffraction. The nanoindentation tests measured the elastic modulus (Em) and hardness (H). Biaxial flexural strength was performed, and Weibull statistics were used to determine the characteristic strength and Weibull modulus. The probability of survival was also determined. The Em and H data were analyzed by one-way ANOVA and Tukey test. Results: Diffractograms revealed the presence of monoclinic phase in both materials after aging. The hydrothermal reactor decreased the Em for ATZ compared to its immediate condition; and the H for both ATZ and 3Y-TZP regarding their immediate and autoclave aging conditions, respectively. The aging protocols significantly increased the characteristic strength for ATZ, while decreased for 3Y-TZP. No difference regarding Weibull modulus was observed, except for 3Y-TZP aged in reactor. For missions of up to 500 MPa, both materials presented a high probability of survival (>99 %) irrespective of aging condition. Significance: The synthesized ATZ composite exhibited greater physical and microstructural stability compared to 3Y-TZP, supporting potential application of the experimental material for long-span reconstructive applications.

© 2024 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.Modern dry pressing of ceramic powders using spray-dried granulates cannot avoid the occurrence of defects related to persisting inter- and intra-granulate interstitial voids. These constitute the parent defect size population limiting the application of polycrystalline ceramics in high-stress conditions. The mitigation of such defects could widen the range of application in technical and biomedical engineering, reduce the safety range for design, and extend the lifetime of components. Herein, the Weibull size-effect on strength in size-partitioned Yttria-stabilized zirconias (YSZ) feedstocks is used to explore the viability of changing the density distribution of granulate sizes as an effective strategy to obtain a denser particle packing that could reduce the size distribution of strength-limiting pressing defects. In a direct assessment of critical defect size using multiscale strength testing with a dataset of ≈1300 values, the success of such an approach in increasing the strength reliability for small volume components is demonstrated, along with its ultimate failure in altering the defect size distribution in sintered YSZ ceramics across several length scales. Finally, it is shown that granule morphology (spherical or dimpled) fails to affect the defect density and size distribution in YSZ ceramics.

© 2024 Wiley Periodicals LLC.Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibers embedded with borate glasses of 45B5 composition doped with Co2+, Cu2+, and Zn2+(46.1 B─O3-26.9-X CaO-24.4 Na─O-2.6 P─Os, X CoO/CuO/ZnO mol % (X = 0–5)) were produced by electrospinning for wound healing applications. Prior to their addition, the glasses exhibited two broad halos typical of a vitreous borate network, which were mainly composed of ring-type metaborate structural units. The particle distribution in the PHBV nanofibers embedded with 45B5 borate bioactive glasses is present in isolated and agglomerated states, being partially coated by a polymeric layer—except for the cobalt-doped glass, which resulted in a successful encapsulation with 100% embedding efficiency. The incorporation of the glasses reduced the PHBV crystallinity degree and its decomposition temperature, as well as its mechanical properties, including Young's modulus, tensile strength, and elongation at break. The neat PHBV fibers and those containing the cobalt-doped glasses demonstrated great cytocompatibility with human keratinocytes (HaCat), as suggested by the high cell viability after 7 days of exposure. Further studies are needed to fully understand the wound healing potential of these fibers, but our results significantly contribute to the area.

© 2024Conductive inks are essential components in electronics as they enable the printing of electronic circuits and components on diverse surfaces. Furthermore, they can be easily tailored to enhance chemical bonding with specific targets in sensing devices. This technology plays a crucial role in the development of both rigid and wearable sensors. Conductive inks for printed electronics and sensor devices should possess several key characteristics, including high conductivity, flexibility, affordability, and compatibility with various substrates. However, conventional conductive inks based on metal nanoparticles tend to be expensive and lack flexibility. This study aims to produce a conductive ink comprised of carbon-black-derived flash graphene (CBFG) and poly(o-methoxy aniline) (POMA), which can be applied to electronic devices. The structures and morphology of both precursors were assessed, and the electrical conductivity of ink coatings containing CBFG, POMA, and a combination of both was investigated. The effect of each component's concentration on the ink's electrical conductivity (EC) was investigated using a 23 factorial design of experiment. In conclusion, the most conductive film presented an EC of approximately 0.768 S m−1 when the concentrations of graphene, POMA, and binder were 40.0, 2.0, and 4.0 mg L−1, respectively. While further research is needed to explore the flexibility and adhesion properties of the ink on different substrates, our solvent and organic-based conductive ink offer environmental benefits and boost sensor performance.

© 2024 by the authors.This study focuses on the cytotoxic evaluation of functionalized multi-walled carbon nanotubes (MWCNT) and microbial biofilm formation on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocomposites incorporating MWCNTs functionalized with gamma-aminobutyric acid (GABA) and carboxyl groups. The materials were characterized for cytotoxicity to fibroblasts and antimicrobial effects against Escherichia coli, Staphylococcus aureus and Candida albicans. The functionalization of MWCNTs was performed through oxidation (CNT-Ox) and GABA attachment (CNT-GB). The PHBV/CNT nanocomposites were produced via melt mixing. All MWCNT suspensions showed non-toxic behaviors after 24 h of incubation (viability higher than 70%); however, prolonged incubation and higher concentrations led to increased cytotoxicity. The antibacterial potential of PHBV/CNT nanocomposites against S. aureus showed a reduction in biofilm formation of 64% for PHBV/CNT-GB and 20% for PHBV/CNT-Ox, compared to neat PHBV. Against C. albicans, no reduction was observed. The results indicate promising applications for PHBV/CNT nanocomposites in managing bacterial infections, with GABA-functionalized CNTs showing enhanced performance.

© 2024 Elsevier LtdThe development of a novel TiO2/KNbO3/g-C3N4 photocatalyst for the degradation of sulfamerazine under artificial sunlight was investigated in this study, aiming to obtain a highly effective material through the formation of Z-scheme heterojunctions between the proposed semiconductors. The characterizations confirmed the formation of the intended heterojunctions in the ternary composite photocatalyst, as the presence of TiO2, KNbO3 and g-C3N4 was successfully verified. Furthermore, the coupling between the semiconductors in the form of the ternary photocatalyst led to structural, morphological, and optical modifications of the TiO2 base matrix, such as a higher specific surface area and larger visible light absorption. The optimized ternary material (TiO2-5% KNbO3-0.25% g-C3N4) exhibited the highest reaction degradation capacity for the sulfamerazine (SFMZ) in both solar (86.5% degradation) and visible light (60% degradation) tests, confirming a significant enhancement over the pure TiO2, which achieved 48% degradation under solar light and 10% degradation under visible light. This result was mainly attributed to the formation of Z-scheme heterojunctions between the semiconductors, which enhanced the charge-transport efficiency during photonic excitation. Lastly, the degradation pathway proposed using mass spectroscopy analysis indicated the formation of mainly less toxic intermediates, as estimated through quantitative structure-activity relationship (QSAR) predictions.

© 2024 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals LLC.The field of tissue engineering has witnessed significant advancements in recent years, driven by the pursuit of innovative solutions to address the challenges of bone regeneration. In this study, we developed an electrospun composite scaffold for bone tissue engineering. The composite scaffold is made of a blend of poly(L-lactide-co-ε-caprolactone) (PLCL) and polyethylene glycol (PEG), with the incorporation of calcined and lyophilized silicate-chlorinated bioactive glass (BG) particles. Our investigation involved a comprehensive characterization of the scaffold's physical, chemical, and mechanical properties, alongside an evaluation of its biological efficacy employing alveolar bone-derived mesenchymal stem cells. The incorporation of PEG and BG resulted in elevated swelling ratios, consequently enhancing hydrophilicity. Thermal gravimetric analysis confirmed the efficient incorporation of BG, with the scaffolds demonstrating thermal stability up to 250°C. Mechanical testing revealed enhanced tensile strength and Young's modulus in the presence of BG; however, the elongation at break decreased. Cell viability assays demonstrated improved cytocompatibility, especially in the PLCL/PEG+BG group. Alizarin red staining indicated enhanced osteoinductive potential, and fluorescence analysis confirmed increased cell adhesion in the PLCL/PEG+BG group. Our findings suggest that the PLCL/PEG/BG composite scaffold holds promise as an advanced biomaterial for bone tissue engineering.

© 2024This study aimed to compare two different compositions of sol-gel method-derived silicate chlorinated bioactive glasses - 45S5 and 58S - and explore the dehydration processes applied (lyophilization, lyophilization+calcination, and calcination). In the synthesis process, sodium metasilicate was used as a silica precursor, and it underwent ion exchange to form silicic acid. The samples underwent characterization through a variety of techniques, assessing their structural properties including Raman spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy, and regarding its bioactivity by the apatite mineralization assay in simulated body fluid. Raman spectroscopy revealed the lyophilization process led to the formation of Q1, Q2, and Q3 silicate structural units for both glasses, but following calcination these reacted to form solely Q2 units - as in the calcined-only glasses. X-ray diffraction analysis confirmed the amorphous nature of the 58S glass, while the 45S5 glass exhibited strong crystalline reflections, including a characteristic peak of sodium chloride. The apatite mineralization assay proved the high bioactivity of the produced glasses. The lyophilized only exhibited rapid hydroxyapatite conversion as a reflection of their structural units containing Q1 structures and of their porous microstructure. The calcined and lyophilized-calcined glasses formed calcium phosphate chloride (Ca2PO4Cl) as an intermediated phase in the glass conversion process. For the 45S5 glass in which both dehydration processes were applied, the intermediated phase led to pH equilibrium of the SBF solution. These findings contribute to the understanding of the structural and compositional properties of silicate chlorinated bioactive glasses synthesized via the sol-gel method. The evaluated glasses show potential for use in bone regeneration applications, with their bioactivity and structural characteristics playing key roles in promoting tissue healing and bonding with bone.

© 2024 Wiley Periodicals LLC.Zirconia implants are gaining attention as a viable alternative to titanium implants due to their comparable osseointegration development, improved soft tissue adaptation, and enhanced aesthetics. An encouraging avenue for improving zirconia implant properties involves the potential application of bioactive coatings to their surfaces. These coatings have shown potential for inducing hydroxyapatite formation, crucial for bone proliferation, and improving implant mechanical properties. This study aimed to evaluate the effect of coating zirconia implants with two bioactive glasses, 45S5 and BioK, on osteogenesis in vitro and osseointegration in vivo. Zirconia samples and implants were prepared using Zpex zirconia powder and blocks, respectively. The samples were divided into three groups: polished zirconia (ZRC), zirconia coated with 45S5 bioglass (Z + 45S5), and zirconia coated with BioK glass (Z + BK). Coatings were applied using a brush and sintered at 1200°C. Chemical analysis of the coatings was carried out using x-ray diffraction and Fourier Transform Infrared Spectroscopy. Surface topography and roughness were characterized using scanning electron microscopy and a roughness meter. In vitro experiments used mesenchymal cells from Wistar rat femurs, and the coated zirconia implants were found to promote cell viability, protein synthesis, alkaline phosphatase activity, and mineralization, indicating enhanced osteogenesis. In vivo experiments with 18 rats showed positive results for bone formation and osseointegration through histological and histomorphometric analysis and a push-out test. The findings indicate that bioactive glass coatings have the potential to improve cell differentiation, bone formation, and osseointegration in zirconia implants.

© 2023 Elsevier LtdThis study aimed to develop a recycling process for the remnants of milled 3Y-TZP and enhance their properties using glass infiltration. 3Y-TZP powder was gathered from the vacuum system of CAD–CAM milling equipment, calcined and sieved (x < 75 μm). One hundred twenty discs were fabricated and pre-sintered at 1000 °C/h. These specimens were then divided into four groups, categorized by glass infiltration (non-infiltrated [Zr] or glass-infiltrated [Zr-G]) and sintering temperature (1450 °C [Zr-1450] or 1550 °C [Zr-1550]/2h). After sintering, the specimens were characterized by X-Ray Diffraction (XRD), relative density measurement, and scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). The biaxial flexural strength test was performed according to the ISO 6872 and followed by fractographic analysis. Subsequent results were analyzed using Weibull statistics. Relative density values of the sintered specimens from Zr-1450 and Zr-1550 groups were 86.7 ± 1.5% and 92.2 ± 1.7%, respectively. Particle size distribution revealed particles within the range of 0.1–100 μm. XRD analysis highlighted the presence of the ZrO2-tetragonal in both the Zr-1450 and Zr-1550 groups. Glass infiltration, however, led to the formation of the ZrO2-monoclinic of 9.84% (Zr-1450-G) and 18.34% (Zr-1550-G). SEM micrographs demonstrated similar microstructural characteristics for Zr-1450 and Zr-1550, whereas the glass-infiltrated groups exhibited comparable infiltration patterns. The highest characteristic strength was observed in the glass-infiltrated groups. Fractographic analyses suggested that fracture origins were related to defects on the tensile side, which propagated to the compression side of the samples. Both the sintering temperature and glass infiltration significantly influenced the mechanical properties of the 3Y-TZP recycled.

© (2024), (Sociedade Brasileira de Hematologia e Hemoterapia). All rights reserved.This study evaluated the effect of different occlusal surface finishes (glaze and silica glass infiltration) on surface characteristics and fatigue behavior of partially stabilized zirconia (PSZ) plates adhesively bonded onto epoxy resin discs. PSZ disc specimens (n = 15; Katana blocks STML, Kuraray Noritake Dental) were produced (Ø = 10 mm; thickness = 1.2 mm) and allocated into 3 groups: As sintered (S), silica glass infiltration (SGI), and glaze application (G). The PSZ intaglio surface was air-abraded with 50-μm alumina powder followed by bonding agent application. All produced PSZ were adhesively cemented onto dentin analogue discs made of epoxy resin material (Ø = 10 mm; thickness = 2 mm). Step stress fatigue test was performed (load ranging from 200 to 1800 N; step size 100 N and 10,000 cycles; 20 Hz). The topographic, microstructural, and fractographic analyses were performed by scanning electron microscopy. Results: No statistically significant difference in fatigue behavior was detected among the groups. All failures started at the bonding surface. Silica glass-infiltration and glaze layer application provided a smoothing effect, while the sintered group had a surface with grooves. The occlusal surface finishing method (silica glass infiltration or glazing) had no deleterious effect on fatigue behavior of adhesively bonded PSZ plates.

© 2024 Universidade Federal de Sao Carlos. All rights reserved.Borate bioactive glasses are more soluble than silicate’s and convert rapidly and completely into hydroxyapatite (Ca5(PO4)3(OH)), being more suitable for wound healing applications than their silicate counterparts. In this work, the 45B5 composition (46.1 B2O3 – 26.9 CaO – 24.4 NaO – 2.6 P2O5, mol%)) were embedded into electrospun PHBV (Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)) nanofibers by encapsulation and/or electrospray deposition aiming to produce a wound dressing with optimized bioactivity and antibacterial properties for wound healing applications. The fibers were characterized regarding their physical, structural, and thermal properties, and in vitro by L929 Mouse Fibroblast Cell Line adhesion, migration, and cytotoxicity and by its antibacterial activity against the bacteria S. aureus. The set of characterizations evidences that the encapsulation method was the most promising for the 45B5 embedding into PHBV nanofibers, as it produced a wound dressing with great loading efficiency (70%) with a highly hydrophilic surface, leading to expressive adhesion, migration, and viability of L929 cells and antibacterial activity. Thus, the nanofibers produced by the encapsulation method alone provided a dressing with high potential in wound healing management.

© (2024), (Sociedade Brasileira de Hematologia e Hemoterapia). All rights reserved.Borosilicate glass was developed to enhance the mechanical behavior and smoothness of dental zirconia as an alternative to conventional glaze. This study assessed the mechanical and optical properties of 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) coated with borosilicate glass or a commercial glaze fired for an extended period of time. Disc-shaped 3Y-TZP zirconia specimens (Zpex, Tosoh) were sintered at 1550°C for 2 hours. The specimens were divided into three groups: as-sintered (control, C); commercial glaze (G); and borosilicate glass (SL). The glaze and borosilicate glass were applied over the zirconia and fired for 20 minutes at 950°C and 1200°C, respectively. Biaxial flexural strength, fractography, X-ray diffraction (XRD), roughness (Ra and Rz), fracture toughness (Vickers indentation method), color difference (∆E00), and translucency (TP00) analyses were conducted. The t-test or the one-way ANOVA and Tukey’s tests were used to analyze the data (α = 0.05). Flexural strength data were subjected to the Weibull analysis. The SL group exhibited the highest flexural strength (1025.8 MPa), whereas the C (859.41 MPa) and G (816.0 MPa) groups exhibited similar values. The SL group also had the highest characteristic strength. The fracture origin in all groups was on the zirconia surface. XRD analysis revealed that the specimens from the SL group contained tetragonal, cubic, and monoclinic phases. The SL group presented the lowest surface roughness. Fracture toughness in the SL group was lower than in the C group, but similar to that observed in the G group. The translucency and color differences observed in the G and SL groups were similar. Borosilicate glass enhanced the flexural strength of 3Y-TZP, promoted the smoothest surface, and exhibited optical properties similar to those of the glaze.

© 2023 Elsevier B.V.This paper explores the application of cross-linked cellulose beads as a sustainable and cost-effective support for the ZnO/SnO2/carbon xerogel hybrid photocatalyst. The application of the developed photocatalytic beads, named CB-Cat, was directed at a simultaneous adsorption/photocatalysis process, which was carried out under simulated sunlight. The characterization of the CB-Cat indicated a good dispersion of the photocatalyst of choice throughout the cellulose matrix, confirming its incorporation into the cellulose beads. Furthermore, it is possible to observe the presence of the photocatalyst on the surface of the CB-Cat, confirming its availability for the photonic activation process. The results showed that the simultaneous adsorption/photocatalysis process was optimal for enhancing the efficiency of methylene blue (MB) removal, especially when compared to the isolated adsorption process. Additionally, the regeneration of the CB-Cat between cycles was favorable toward the maintenance of the MB removal efficiency, as the process carried out without regeneration displayed significant efficiency drops between cycles. Finally, the mechanism evaluation evidenced that hydroxyl and superoxide radicals were the main responsible for the MB photocatalytic degradation during illumination with simulated sunlight.

© 2023 Wiley Periodicals LLC.Objective: To evaluate the effect of different hydrofluoric acid concentrations and etching times on the surface, chemical composition and microstructure of lithium disilicate. Material and Methods: Ninety specimens of pressed lithium disilicate (LDS) were obtained (IPS e.max Press, Rosetta SP and LiSi Press). The specimens of each material were divided in two groups according to the hydrofluoric acid concentration: 5% and 10% (n = 15/group), and subdivided according to the etching time: 20, 40 and 60 s (n = 5/group). Crystalline evaluations and chemical composition were performed through x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), respectively. Microstructural analyses were performed by scanning electron microscope (SEM), surface roughness (Ra), and material thickness removal evaluation. Thickness removal and Ra data were analyzed by ANOVA and Tukey test (p < 0.05). Results: XRD demonstrated characteristic peaks of lithium disilicate crystals, lithium phosphate and of a vitreous phase for all materials. EDS identified different compositions and SEM confirmed different surface responses to acid etching protocols. Material and etching time influenced Ra and material thickness removal (p < 0.05). Conclusion: Hydrofluoric acid concentration and etching time affect the surface characteristics of LDS differently. LiSi Press presented higher resistance to hydrofluoric acid etching compared to e.max Press and Rosetta SP. Clinical Significance: Applying the appropriate etching protocol is pivotal to avoid excessive material removal and to prevent jeopardize the mechanical and optical properties of the material.

© 2023 Wiley Periodicals LLC.The development of bioactive membranes with bone repair properties is great interest in the field of tissue engineering. In this study, we aimed to fabricate and characterize a composite membrane composed of sol–gel synthesized bioceramics and electrospun polycaprolactone (PCL) fibers for bone tissue regeneration applications. The bioceramics were prepared using the sol–gel method with nitrate (N) and chloride (CL) as precursors. PCL and bioceramic solutions were electrospun to obtain ultrafine fiber mats. Raman spectroscopy, x-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were used to characterize the materials. The results showed that both chlorinated and non-chlorinated bioceramics contained NBOs (non-bridge bonds) and crystallized the α-wollastonite phase, with the chlorinated version doing so at lower temperatures. In vitro tests were performed to evaluate cytotoxicity, cell adhesion, and mineralized matrix formation on the membranes. The composite membranes showed improved cell viability and promoted mineralization nodules formation. This study presents a promising approach for the development of bioactive membranes for bone tissue engineering, with potential applications in bone regeneration therapies.

© 2024 The Author(s)Thermal storage systems are essential for optimizing energy resource utilization, particularly in the current context where sustainability and efficiency are critical. Phase Change materials (PCMs) offer a promising solution for improving thermal management efficiency without additional power consumption. Considering that the low thermal conductivity of phase change materials (PCMs) is a limiting factor for heat transfer, this study employs the enthalpy-porosity method to analyze the melting characteristics of a high-Prandtl number PCM. Additionally, this study investigated the effect of varying the number of fins in the heat sink on the heat transfer rate. The material melting process was modeled by considering buoyancy effects and treating the flow as incompressible, Newtonian, transient, and laminar. Lauric acid was selected as the working material with temperature-dependent properties that were incorporated into the simulations for greater accuracy. Three different heat sink configurations were analyzed, varying the number of fins from 5 to 10 and their lengths from 0.02 m to 0.04 m. The objective was to optimize the cooling performance using aluminum, which was selected for its excellent balance of lightweight properties and high thermal conductivity. This analysis aimed to assess how these variations in the fin count and dimensions affect the overall heat dissipation efficiency and thermal management of the system. The inclusion of a finned heat sink within a heat exchanger has demonstrated significant efficiency, particularly in regions with substantial boundary layer development, resulting in enhanced heat transfer. These findings highlight the effectiveness of using finned heat sinks in these regions. However, an interesting observation emerged regarding the effect of increasing the number of fins over long periods. Although initially beneficial, a larger number of fins eventually led to a reduced performance over time, notably affecting the thermal storage capacity and molten liquid mass production. Additionally, this study elucidates the influence of natural convection on thermal boundary layer development, highlighting the complexity of the heat transfer processes.

© 2024 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.Decarbonization of the aviation sector is a key factor for current and future systems. Waste Heat Recovery (WHR) may be used to convert waste energy to electric power by using a bottoming cycle, which can reduce the overall fuel requirement of the airplane. One of the potential bottoming cycles for aircraft application is a Supercritical CO2 (sCO2) power system. The sCO2 power system has advantages because of the component compactness, which is crucial for aircraft integration. However, the main challenge for aircraft integration is the size and weight of the heat exchangers. The present work focuses on the performance of the Supercritical CO2 power system in both current and next-generation aircraft engines considering an innovative and advanced design of the sCO2 heat exchangers (cooler and primary heat exchanger). The first part of the work is focused on the analysis of the sCO2 WHR system for an aircraft engine. The second part of the work is focused on a detailed heat exchanger selection, design and optimization based on the aircraft engine parameters. The results show the potential of WHR utilization, which may generate an additional 100 - 200 kW. However, the heat exchangers may increase overall weight of the aircraft. For this reason, an advanced design is necessary.

© 2024 Elsevier LtdThe global increase in food demand drives the need for efficient and sustainable agricultural practices, particularly in the energy-intensive process of grain drying, which is crucial for maintaining product quality. This study proposes the exergetic and environmental analysis of a hybrid electric column dryer for soybeans, comparing its performance across four distinct national contexts: Paraguay, Brazil, the United States, and China. The aim is to explore how different energy matrices and degrees of hybridization influence the energy and environmental costs associated with soybean drying. In addition to considering different energy matrices, the present study advances beyond previous research by coupling the mathematical drying model with thermodynamic analysis. By integrating these aspects, it is possible to conduct thorough simulations and gain insights into the exergetic, environmental, and economic impacts of the drying process. For this, a computational model was developed capable of simulating the drying process of soybeans and determining the conditions of grains and air at the exit of the drying chamber and, thus, performing the First and Second Law analyses with different degrees of hybridization for four countries with different electricity mixes. Results reveal that for thin-layer soybean drying dynamics at T = 80 °C and v = 0.5 m/s, approximately 68.2 min were needed to reduce grain moisture content from 18% w.b (0.22 d.b) to 14% (0.163 d.b), with outlet temperatures of θ = 67.57 °C for grains and T = 71.7 °C for air. The final water content of the drying air was 0.021 kgw/kga. Exergetic cost analysis revealed significant variations among countries, with Paraguay exhibiting the greatest difference between completely fossil and purely electrical cases (433.5 kJ/kgg). Environmental cost analysis showed substantial differences in electrical energy use for drying, particularly in countries with predominantly renewable energy matrices. Paraguay showed the highest emissions variation with a purely electrical system, differing by 27.55 gCO2/kgg compared to the pure fossil case. Brazil, the United States, and China had differences of 25.33, 17.4, and 11.90 gCO2/kgg, respectively. From an economic standpoint, hybridization was found to be unfeasible in Brazil due to high electricity prices, while theoretically favorable in China, Paraguay, and the United States. Paraguay had the lowest drying cost at 2.63 US$/tong, followed by China, the United States, and Brazil with 3.92, 4.74, and 15.79 US$/tong, respectively. These analyses underscore the importance of comprehensive studies in evaluating process hybridization. Considering electricity mix composition and reliable life cycle analysis data is crucial for obtaining meaningful results. Integrated exergetic, environmental, and economic analyses are essential for guiding energy use decision-making processes.

© 2023 Elsevier Masson SASThe current work aims to understand and model thermal runaway (TR) events in lithium-ion (LIB) 18650 cells within the context of aircraft battery applications. The primary goal is to comprehend the phenomenon and discuss strategies for mitigating its consequences during aircraft operation. TR is modeled using Arrhenius kinetic equations and is implemented in both lumped parameters (Matlab SimulinkTM), and 3D CFD simulations (Ansys FluentTM) using User Defined Functions. To validate the thermochemical model, cells are initially simulated in an oven test, where a cell is exposed to a temperature-controlled atmosphere, triggering exothermic reactions. With a strong correlation between lumped parameters and 3D models, the latter is simulated under battery module installation conditions. An internal short-circuit is then implemented within the cell to observe how thermal runaway is triggered by an internal heat source. The trigger cell is subsequently placed in a battery module assembly to assess the dominant heat transfer modes and the likelihood of TR induction from one cell to its neighbors. This work's main objective and innovation are to compare different materials in which cells are immersed while observing the main heat transfer parameters for each material. Three conditions are tested: ceramic paper fiber and G7 as solid separators, and no separator material, where air fills the gaps between cells. The analysis of heat transfer modes reveals radiation's dominance in the case of air interstice, suggesting the possibility of using a special coating to reduce the cell surface emissivity as an alternative to decrease the likelihood of TR propagation. Thus, two values of surface emissivity were tested in the case of air. Considering a cell triggered by an internal short-circuit, a thermal runaway temperature spike is not observed in any of the four cases. However, the air interstice case with regular emissivity is the most critical one, with the closest cell reaching peak temperatures as high as 136 °C in 490 s. The ceramic paper fiber is considered the best separator material, as it postpones the temperature increase in the closest cell while also being lighter than G7. The results and discussions concerning heat propagation presented herein can serve as guidelines for developing strategies to mitigate thermal runaway in battery modules.

© 2023, Emerald Publishing Limited.Purpose: The purpose of this paper is to present a practical data-based framework for the prioritization of investment in manufacturing technologies, methods and tools, and to demonstrate its applicability and practical relevance through two case studies of manufacturing firms of different industrial segments. Design/methodology/approach: The proposed framework is based on network theory applied on technology adoption. For this, the database of Industry 4.0 maturity assessments of SENAI was used to develop data visualization tools named “Technology Networks”. Thus, this study is descriptive research with correlational design. Besides, the framework was applied in two companies and semi-structured interviews were carried out with domain experts. Findings: The technology networks highlight the technological adoption patterns of six industrial segments, by considering the answers of 863 Brazilian companies. In general, less sophisticated technologies were positioned in the center of the networks, which facilitates the visualization of adoption paths. Moreover, the networks presented a well-balanced adoption scenario of Industry 4.0 related technologies and lean manufacturing methods and tools. Research limitations/implications: Since the database was not built under an experimental design, it is not expected to make statistical inferences about the variables. Furthermore, the decision to use an available database prevented the editing or inclusion of technologies. Besides, it is estimated that the technology networks given have few years for obsolescence due to the fast pace of technological development. Practical implications: The framework is a tool that may be used by practicing manufacturing managers and entrepreneurs for taking assertive decisions regarding the adoption of manufacturing technologies, methods and tools. The proposition of using network theory to support decision making on this topic may lead to further studies, developments and adaptations of the framework. Originality/value: This paper addresses the topics of lean manufacturing and Industry 4.0 in an unprecedented way, by quantifying the adoption of its technologies, methods and tools and presenting it in network visualizations. The main value of this paper is the comprehensive framework that applies the technology networks for supporting decision making regarding technology adoption.

© 2024The aviation industry accounts for part of the CO2 emissions contributing to climate change. The industry has established a target to reduce 2050 net aviation carbon emissions by 50 % relative to 2005 levels. With this in mind, waste heat recovery is a key pathway to achieve reduced emissions and improve system efficiency. The waste heat may potentially be converted to electric power using a supercritical CO2 Brayton power cycle. The sCO2 power system offers the advantage of compactness owing to the high working fluid density, which is an important consideration for aircraft performance. The present work focuses on the integration of the sCO2 power system into the aircraft propulsion system and evaluation of its performance. Detailed optimization of the sCO2 waste heat system will be evaluated with a focus on cycle efficiency and net power under different operating conditions, including ground, takeoff, climb, cruise, and landing operations. The study is divided into two parts with two different turbofan engines, one with a nominal thrust of 30 kN and the other with a nominal thrust of 9 kN. The first part shows the effect and operation of the waste heat recovery unit under the different operating conditions. The second part is focused on cycle optimization and performance evaluation. The results demonstrate the potential of waste heat recovery during a range of operational conditions. The sCO2 cycle efficiency can reach between 25 and 39 % (depending on aircraft engine) with net power output in the range of 100 to 260 kW.

© 2024 by the authors.The internal losses in the tip clearance region strongly influence the compressor performance and its operational range. Previous research proved that passive wall treatments with circumferential grooves in axial compressors effectively increase the compressor stall margin. The vortex generated inside the circumferential grooves creates a resistance to the flow that leaks into the tip clearance region of the compressor. However, most works found in the literature on circumferential grooves in axial compressors deal only with high-performance single-stage axial compressors. Therefore, there is a need to investigate and analyze the behavior of circumferential grooves in a multi-stage environment. In the present work, a passive wall treatment with circumferential grooves was implemented in a multi-stage axial compressor. Different configurations of circumferential grooves were created at the casing of the first and second rotor rows used in a four-stage axial flow compressor. Numerical simulations were performed to evaluate the influence of the circumferential grooves on the performance of a multi-stage axial compressor. The results obtained after the simulations for the different circumferential groove configurations were compared with the results obtained for the compressor without casing treatment (smooth wall) for different rotational speeds. Furthermore, the complete compressor map characteristics were simulated for the different casing treatment configurations, and the results were compared with the compressor characteristics of the smooth wall case. The passive wall treatment with circumferential grooves produced changes in the multi-stage axial compressor flow field, especially in the tip clearance region, improving the compressor stability mainly for part load speeds.

©2024 Luiz Vitor Tozi, João Vidal, Jesuino Takachi Tomita, Anderson Vicente Borille, Cleverson Bringuenti, Alexandre Roma, Henrique Rodrigues Oliveira.The industry and the academy are continuously developing new technologies and approaches regarding the gas turbine manufacturing. Logically, sectors of turbomachinery and aerospace engineering are deeply focused on applying newer and even unconventional manufacturing process, aiming on cost reduction, reduced lead times and efficiency. In addition, it is conspicuous that metal additive manufacturing (AM) technologies can provide interesting possibilities for companies seeking to innovate and perfect existing components, with respect to reach better buy-to-fly ratios. In this paper, the authors developed a proposal for additively manufacturing a fuel swirler and evaluated in detail its process of fabrication in order to compare the results with the characteristic of a conventionally manufactured swirler. Furthermore, a dedicated review of the state-of-the-art related to the AM of fuel swirlers were realized to evaluate the relevance of this topic to conclude if the use of AM to fabricate this component can favor the aerospace industry.

© 2024 Tiago Andrei Adamczevski, Luiz Vitor Tozi, João Guilherme Vidal do Nascimento, Cleverson Bringhenti, Jesuíno Takachi Tomita.This paper presents the development of a gas turbine simulator based on an application of a real turbogenerator used to generate electricity on an offshore oil platform, the configuration is a turboshaft with free power turbine. The compressor, turbines and the control system were developed using specific methodologies. The development of the simulator was done using the Simulink environment in Matlab®. The development was done using blocks to represent each one of the main components in the engine. A stage stacking methodology based on the real geometry for each stage was adopted to create the compressor maps. The map was used in lookup tables blocks with help of auxiliary coordinates, also known as beta lines. To model both turbines were applied an ellipse equation also known as Stodola’s law. The engine simulator model was tested in an open loop and the results evaluated with the manual data from the engine.

© 2024 by ASME.This work aims to provide a methodology for defining the design point for industrial gas turbine considering the economic, environmental, and engine performance aspects. The definition of the design point is a key step in the development project of a gas turbine since this definition involves the analysis of several operational points to verify if the desired performance can be obtained. Thus, to extend the methodology presented in the literature developed for micro-turbines to consider industrial gas turbines a computer program was developed in MATLAB®. This program is capable of performing thermodynamic calculations for design point definition and of performing single- and multi-objective thermoeconomic and thermodynamic optimizations using genetic algorithms. For the optimization process, total cost minimization, yield maximization, and gas turbine-specific work maximization were chosen as objective functions. The decision variables chosen were compressor pressure ratio, compressor polytropic efficiency, turbine polytropic efficiency, and maximum cycle temperature. For the calculation of economic aspects, fixed costs (equipment, installations, land acquisition cost, etc.) and variable costs (fuel, emissions, and operation and maintenance costs) were considered. The emission cost of NOx, CO, and UHC was considered for the environmental cost calculations. The thermodynamic calculations were based on enthalpy and entropy. The developed computer program was validated by simulating a commercial gas turbine and comparing the results obtained, also using a commercial program, GASTURB®. The presented optimization process shows results for a single objective, two objectives, and three objectives, where the results show a comparison between different design points obtained. The software developed will be of great assistance in the learning of engineering students.

© 2024 by ASME.The air conditioning system of executive, commercial, or military aircraft heavily relies on air cycle machines due to the availability of engine bleed air and their lightness and reliability compared to vapor cycle systems. The type of application, weight, refrigeration capacity, financial aspects, size, performance, and other specific design requirements drive the selection of suitable equipment for a particular aircraft. The motivation of this paper has been based on summarize the main concepts of the aeronautical environmental control system, as well as the mathematical aspects underlying the modeling of a simple/bootstrap air cycle unit in a software. The main aim is to develop software that can generate high level requirements that would be refined during the development phase of an aeronautical air conditioning system. It will be greatly benefit for engineers and students in the design of aeronautical air conditioning systems to better understand and to meet the design requirements. The results demonstrate the influence of the water-sprayer and chilled-recirculation system on air cycle performance and cabin inlet temperature, respectively. They also show changes in certain parameters of interest such as a function of altitude, power consumed by the secondary compressor, and air cycle machine fan. The computational model has proven to be a useful tool for performing parametric studies and evaluating critical points in designing and selecting an air conditioning unit based on a simple/bootstrap air cycle with humid air (any quantity of moist) as the working fluid.

© 2024 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.Decarbonization of the aviation sector is a key factor for current and future systems. Waste Heat Recovery (WHR) may be used to convert waste energy to electric power by using a bottoming cycle, which can reduce the overall fuel requirement of the airplane. One of the potential bottoming cycles for aircraft application is a Supercritical CO2 (sCO2) power system. The sCO2 power system has advantages because of the component compactness, which is crucial for aircraft integration. However, the main challenge for aircraft integration is the size and weight of the heat exchangers. The present work focuses on the performance of the Supercritical CO2 power system in both current and next-generation aircraft engines considering an innovative and advanced design of the sCO2 heat exchangers (cooler and primary heat exchanger). The first part of the work is focused on the analysis of the sCO2 WHR system for an aircraft engine. The second part of the work is focused on a detailed heat exchanger selection, design and optimization based on the aircraft engine parameters. The results show the potential of WHR utilization, which may generate an additional 100 - 200 kW. However, the heat exchangers may increase overall weight of the aircraft. For this reason, an advanced design is necessary.

© 2024 Elsevier B.V.This work presents the synthesis and characterization of a multicomponent mesoporous bioactive glass (MMBG) derived from the composition of 58S glass modified with copper, zinc, and boron. Morphological data revealed the presence of spherical particles with an average size of 616 nm and a specific surface area of 295 m2·g−1. X-ray diffractogram analysis confirmed the lack of long-range order in the MMBG, indicating the presence of a disordered vitreous structure characteristic of glass. The structural scenario of the bioactive glass MMBG reveals a characteristic configuration of borosilicate glasses, where the [BO4] polyhedra, along with SiO4 tetrahedra, constitute the backbone of the glassy matrix. Concerning zinc and copper ions, they function similarly to calcium in compensating for the remaining negative charges within the borosilicate network, behaving as typical network-modifying ions. The presence of these heavy ions, coupled with the formation of the borosilicate network in MMBG, led to a 20 % increase in density compared to 58S glass. Additionally, alterations in the chemical composition and structure of MMBG resulted in a reduction in molar volume compared to 58S, indicating a decrease in the volume occupied by one mole of oxygen in the glass matrix, thereby increasing the oxygen packing density. The pH studies reveal that changes in the chemical composition of MMBG did not compromise its chemical reactivity in aqueous environments. The capability of MMBG glass to act as a bioactive agent for ion therapy is evidenced by its ability to deliver Zn and Cu ions, as substantiated by the gradual disappearance of absorption in wavenumber range of 690–470 cm−1, attributed to the vibration of Zn-O and Cu-O bonds. Preliminary in vitro assay for bioactivity in SBF revealed that the formation of apatite layer on the surface of MMBG glass was notably thicker and denser compared to 58S glass. This result highlights the superior bioactive response of the MMBG bioactive glass, indicating its potential as an exceptionally favorable material for various biomedical applications.

© 2024 American Chemical SocietyThe colon is a main absorption site (nutrients and drugs) and a target for oral therapeutic delivery. However, the latter is challenged by the fact that most drugs degrade during transit in the gastrointestinal tract (GIT). Herein, we rationally designed a universal controlled-release system based on cubosomes contained in microbial nanocellulose capsules that enabled oral administration and pH-triggered delivery of bioactives. We show that the bicontinuous cubosome structure allows the simultaneous incorporation of drugs with differing polarity or surface energy. Furthermore, the multidrug cubosomes combined with the cellulose carrier by in situ biofabrication was demonstrated as a route toward multicomponent 3D capsules with added protection in the GIT. The obtained capsules were subsequently coated with sodium alginate to enable responsiveness, achieving dual cargo-controlled release and site-specific administration. In sum, we successfully engineered pH-responsive, nontoxic microcapsules as a versatile platform for colon-targeted multidrug delivery.

© 2023 Elsevier B.V.The present work presents and discusses the results of a comprehensive electrochemical study of the laser-textured β-Ti12Mo6Zr2Fe (TMZF) alloy coated with a bioactive layer (TMZF-BL), which was strategically designed to produce an improvement in corrosion resistance and impart bioactive properties to the TMZF alloy. The bioactivation of the laser-textured TMZF alloy was performed using a simple and innovative strategy that effectively coated the metal surface with a bioactive layer structured with bioactive glass (BG) particles functionalized with silicate and phosphate groups, acting as chemical anchoring agents. The electrochemical corrosion behavior of the bare and coated TMZF was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in Simulated Body Fluid (SBF) at 37 °C. Our results showed that the presence of the bioactive layer in the TMZF-BL samples shifted the corrosion potential (Ecorr) towards more noble values compared to polished TMZF (TMZF-P), and increased EIS modulus, suggesting that the corrosion resistance improved. The chemical stability of the bioactive coating was confirmed by the high polarization resistance and low capacitance values. Various analysis techniques surveyed the apatite-forming ability and growth on the surface of TMZF-P and TMZF-BL alloys as a function of soaking time in SBF. The bone-like apatite formation rate depended on the homogeneity of the bioactive layer covering the surface of the TMZF-BL alloy. Taken together, our results confirm the success of the experimental strategy designed to bioactivate the TMZF alloy and reinforce the potential of this approach for the development of highly stable bioactive implants, in addition to protecting the alloy surface against corrosion in the physiological environment.

© 2023 Wiley-VCH GmbH.The addition of rare earth elements, such as cerium, to austenitic Fe–Mn–Si-based shape memory alloys has been shown to improve both corrosion resistance and shape recovery. However, the mechanisms underlying the effect of Ce on shape recovery are still unclear. This study investigates the influence of the addition of small amounts of Ce (0.18, 0.42, and 0.96 wt%) on the microstructure and shape recovery of an austenitic Fe–13.50Mn–3.98Si–9.54Cr–4.51Ni alloy. Ce additions induce the formation of a large number of Ce-rich particles, which act as austenitic grain refiners. Both grain refinement and the formation of Ce-rich particles contribute to the strengthening of the matrix at 0.42 wt% Ce addition. In addition, Ce additions alter the MS temperature, which increases with Ce additions. Total shape recovery improves with 0.18 and 0.42 wt% Ce additions, but decreases with 0.96 wt% Ce addition. The beneficial effect of Ce addition in improving the shape recovery of the austenitic Fe–Mn–Si–Cr–Ni alloy is related to the enhancement of the elastic shape recovery component of the total shape recovery. However, the shape memory recovery due to the shape memory effect always decreases with the increase of the Ce content.

© 2024, Academia Brasileira de Ciencias. All rights reserved.Currently, it is crucial for the lubricant formulation industry to explore cost-effective and environmentally friendly methodologies for analyzing the tribological properties of engine aviation lubricants under high-temperature and high-pressure operating conditions. This study demonstrates the feasibility of employing molecular dynamic simulations to gain essential insights into the evolution of the tribological properties of lubricants during operation. A three-layer molecular model was devised, comprising nickel aluminide molecules in the top and bottom layers, and polyol ester in the core. The impact of sliding velocities ranging from 20 km/h to 100 km/h was investigated under varying temperature and pressure conditions. Concentration, temperature and velocity profiles, radial distribution function, mean square displacement, and friction coefficient were calculated and analyzed in detail. Notably, the highest friction coefficients – ranging from 2.5 to 0.75-were observed at the lowest temperature and pressure conditions tested. Conversely, other sections of the gas turbine exhibited substantially lower friction coefficients – ranging from 0 to 0.01.Simulations demonstrate that increasing pressure and temperature reduce polymer chain mobility, leading to stronger internal interactions within the lubricant. Consequently, lubricant adsorption onto metal surfaces decreases. Furthermore, the lubricant performs exceptionally well when its molecules encounter higher velocities and temperatures. Based on the results obtained, the research demonstrates that the presented technique provides both quantitative and qualitative tribological information essential for understanding a system molecular behavior, serving as a guiding framework for researchers in the field.

© The Author(s) under exclusive licence to Associação Brasileira de Engenharia Química 2024.Concrete is a common construction material used to support structures around the world. However, the durability of concrete is affected by weathering action, abrasion, and chemical attack and this may lead to reduction in desired material properties necessary to support structures. Electromigration is the transport of material in a conductor under the influence of an applied electric field. All conductors are susceptible to electromigration; therefore it is important to consider the effects the electrical current resulting from the applied field may have on the conductor. The net force exerted on a single metal ion in a conductor has two opposing contributions: a direct force and wind force. Electrochemical engineering is the branch of chemical engineering dealing with the technological applications of electrochemical phenomena, such as electrosynthesis of chemicals, electrowinning and refining of metals, flow batteries and fuel cells, surface modification by electrodeposition, electrochemical separations and corrosion. This paper presents results of two small-scale tests using electromigration process as a means of transporting nanosilica to recover cement matrix integrity of aged 32 MPa concrete samples extracted from a 40-year-old structure. A set up with two vessel was proposed, with 12 Vdc electrical font working for 48 h generating transportation of nanosilica (12 nm in diameter) into the aged concrete samples. The experiments were performed in two distinct laboratories. One at Flowtest in Brazil and one at the Research Laboratory of the George Mason University Department of Civil Engineering in the US. Thus, repeatability and reproducibility of the process can be proven under laboratory conditions. The success of the electromigration process was verified with electronic microscope (qualitative analysis), scanning electronic microscope, and X ray dispersive energy spectroscopy. The results showed that an electromigration of nanosilica into the cement matrix occurred and resulted in reduction of micro fissures. Additionally, deposition of silica on the sample surface was observed. Reduction of calcium in the matrix was verified with the development of hydrated calcium silicate, providing the recovery of cement matrix in increasing cement mechanical properties like strength and also decreasing the porosity of the concrete matrix. Another important phenomenon is the rehabilitating of the chloride contaminated concrete structure to extend its service life, an electrochemical chloride extraction (ECE) treatment with simultaneous migration of silicate ion was performed. Based on referenced literature, it can be assumed that the extraction of chlorine ions occurs simultaneously with the recovery of cement matrix by nanosilica.

Copyright © 2024 by the International Astronautical Federation (IAF). All rights reserved.Reactive molecular dynamics simulations were utilized to investigate the reaction between ammonium Perchlorate (AP) and aluminum (Al) particles. Two distinct sets of simulations were conducted, one involving a pure aluminum particle and the other featuring a passivated aluminum particle. The aim was to examine and compare the behavior of the reactive systems under different conditions. The simulations were performed using the ReaxFF force field, allowing for a detailed representation of chemical reactions at the atomic scale. Results revealed significant differences in the reaction dynamics between the two systems. The pure aluminum particle exhibited a more rapid and exothermic reaction with AP, leading to a higher release of energy and potentially enhanced propulsion performance. Conversely, the passivated aluminum particle displayed a slower and less exothermic reaction, attributed to the presence of an oxide layer inhibiting direct contact between aluminum and AP molecules. Additionally, kinetic parameters such as reaction rate constants were calculated for both sets of simulations, providing insights into the reaction kinetics of AP-A1 systems. Furthermore, the initial decomposition mechanism of AP was investigated, shedding light on the early stages of the reaction process. These findings provide valuable insights into the role of aluminum passivation in solid rocket propellant formulations and highlight the potential for optimizing energetic materials through molecular-level simulations. Overall, the comprehensive analysis presented in this study advances our understanding of AP-A1 interactions and offers a foundation for further research aimed at enhancing the performance and safety of energetic materials in propulsion applications.

Copyright ©2024 by the International Astronautical Federation (IAF). All rights reserved.Nitramines, like RDX and HMX, are also alternatives to AP as main components in smokeless propellants. They have high specific impulse but are moderately sensitive and have a slightly negative oxygen balance and are therefore unable to contribute positively to the oxygen balance of the propellant. Crystal defects are a constant in applied energetic materials (EMs) and play a crucial role in thermal degradation, combustion and ignition mechanisms, and subsequent aging. Defect engineering is the process of studying how defects affect an EM’s qualities and performances in order to design new EMs that meet the required specifications. An emerging field of study in energetic materials is crystal-defect engineering, which offers previously unheard-of opportunities for regulating physical, chemical, and electrical properties as well as propellants, explosives, and pyrotechnics compositions. There are numerous types of crystal defects, including line defects (dislocation), planar defects (twin, shear band, crack, and surface defect), and volume defects (void). Point defects also include orientational defects and element doping. In this study, ReaxFF molecular dynamics simulations were used to examine the effects of molecule vacancies on the reaction kinetics and thermal decomposition mechanisms of condensed-phase - HMX at different temperatures. The thermal decomposition of HMX is the primary event in the combustion process of solid rocket smokeless propellants, directly affecting the related performance of propellants and even rocket engines. Results showed that three primary initial decomposition mechanisms, namely, NNO2 bond dissociation, HONO elimination, and concerted ring fission, exist at both high and lower temperatures. Molecular vacancies affect how much each of the three pathways contributes to the initial breakdown of HMX, and these effects change with temperature. Molecular vacancies significantly enhance N-N bond cleavage and coordinated ring breaking at high temperatures (3200 K), while impeding the production of HONO bonds. The two main competing reaction pathways are N-N bond dissociation and HONO elimination, with the former being more prevalent during the first breakdown. Additionally, we calculated the first decomposition’s reaction rate constant and activation barriers for various vacancy concentrations. This RMD study showed that molecular vacancies accelerate the decomposition of condensed-phase HMX by increasing the reaction rate constant and reducing activation barriers.

© 2024 The Authors. Published by American Chemical Society.The aluminum industry uses calcined petroleum coke to produce carbon anodes, which act as chemical reducers and electrical conductors in alumina electrolysis. The use of renewable sources could reduce the impacts of fossil materials. In this study, binchotan charcoal was characterized and compared with calcined petroleum coke, with the aim of using it in anode production. The physicochemical properties of the samples were characterized. Binchotan charcoal showed a high fixed carbon and a low ash content. The typical elements of the materials were identified, and high porosity was noted in the charcoal. The thermal behaviors of both materials were alike, and it was noted that charcoal is more influenced by moisture. The charcoal showed higher electrical resistivity compared to coke, and the X-ray diffraction patterns showed the presence of graphite in the samples. The results indicated that binchotan has the potential to partially replace petroleum coke in the aluminum industry.

© 2024 by the authors.Thermally characterizing high-thermal conductivity materials is challenging, especially considering high temperatures. However, the modeling of heat transfer processes requires specific material information. The present study addresses an inverse approach to estimate the thermal conductivity of SAE 1020 relative to temperature during an autogenous LASER Beam Welding (LBW) experiment. The temperature profile during LBW is computed with the aid of an in-house CUDA-C algorithm. Here, the governing three-dimensional heat diffusion equation is discretized through the Finite Volume Method (FVM) and solved using the Successive Over-Relaxation (SOR) parallelized iterative solver. With temperature information, one may employ a minimization procedure to assess thermal properties or process parameters. In this work, the Quadrilateral Optimization Method (QOM) is applied to perform estimations because it allows for the simultaneous optimization of variables with no quantity restriction and renders the assessment of parameters in unsteady states valid, thereby preventing the requirement for steady-state experiments. We extended QOM’s prior applicability to account for more parameters concurrently. In Case I, the optimization of the three parameters that compose the second-degree polynomial function model of thermal conductivity is performed. In Case II, the heat distribution model’s gross heat rate (Ω) is also estimated in addition to the previous parameters. Ω [W] quantifies the power the sample receives and is related to the process’s efficiency. The method’s suitability for estimating the parameters was confirmed by investigating the reduced sensitivity coefficients, while the method’s stability was corroborated by performing the estimates with noisy data. There is a good agreement between the reference and estimated values. Hence, this study introduces a proper methodology for estimating a temperature-dependent thermal property and an LBW parameter. As the performance of the present algorithm is increased using parallel computation, a pondered solution between estimation reliability and computational cost is achieved.

© 2024 Elsevier Inc.AISI 317 L stainless steel replaces 316 L grade in some applications due to its superior mechanical strength and corrosion resistance. Aiming at expanding its applicability to structural applications, ongoing studies are dedicated to overcoming the trade-off between strength and ductility. The stacking fault energy decreases with deformation temperature and favors stacking faulting, (nano)twinning and strain-induced martensite (SIM) formation, resulting in severe microstructural fragmentation. The effect of temperature on deformation behavior of AISI 317 L steel was investigated in samples rolled at room temperature to thickness reductions of 50% and 85% and at 77 K to reductions in thickness of 10% and 50%. The microstructural evolution was followed by scanning electron microscopy, Vickers microhardness, X-ray diffraction, magnetization, electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI). The nucleation sites in the early stages of the transformation sequence γ → ε → α’ were identified in the 10% cryorolled sample. The highest volume fraction of α’-martensite reached 45.8% in the cryorolled steel to 50% rolling reduction. Much lower fractions were obtained for samples rolled to 10% reduction at 77 K (2%) and at room temperature to 50% (0.3%) and 85% reductions (1.6%). The texture components after cryorolling were Goss and Brass for austenite; rotated cube, α- and γ-fibers for δ-ferrite and α’-martensite. The ε-martensite presents the typical texture of hcp metals with a c/a ratio above the ideal value and 〈0001〉 − oriented tilted about 21° from the normal direction towards the rolling direction. The results show cryorolling as an effective method for enhancing SIM formation and promoting severe microstructural refinement in AISI 317 L stainless steel.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.In the present study, the Quadrilateral Optimization Method (QOM) is applied for parameter estimation in an inverse heat transfer problem. A numerical LASER Beam Welding (LBW) experiment of SAE 1020 is the baseline for the estimations. The temperature-dependent thermal conductivity of the steel is assessed. The algorithm accounts for the conductivity as a second-degree polynomial function of temperature. The three parameters of the function are simultaneously assessed. The method regularizes the objective function through Future Time Regularization (FTR) to account for the temporal analysis. Hence, the effect of using different numbers of time steps was analyzed. The most accurate results were found when considering 60 points. Thus, this configuration was set to expand the algorithm to assess the gross heat rate provided by the LASER along with the thermal conductivity function. The results are sensitive enough to represent reliable assessments. Considering the reference and estimated values, the simulated temperatures show good agreement. The present algorithm requires low computational cost due to a GPU’s parallel computation.

© 2024Producer gas from biomass gasification offers a renewable alternative to fossil fuels. However, its low energy density results in low conversion efficiency in engines. Blending producer gas with higher-ranked fuels such as hydrogen has been proposed to overcome this issue. This study investigates the combustion of artificially made producer gas and hydrogen mixtures in an optical SI engine. The molar fraction of hydrogen in producer gas ranged from 14 to 62%, which simulated additions of hydrogen to a low calorific producer gas. The experiments are conducted at a constant speed and stoichiometric ratio. The spark timing is varied to achieve the highest power for each mixture. Results include data on emissions, thermodynamics, and flame morphology. The molar fraction of 33% hydrogen on producer gas improves the flame morphology of the mixture to resemble that of pure natural gas, while 24–36% was found to be the optimal range for engines initially designed to run on natural gas with lower NOx and UHC emissions.

© The Author(s), under exclusive licence to Springer Nature Switzerland AG 2023.The development and implementation of advanced processes to increase the useful life of components are necessary for several industrial segments, once problems such as wear and corrosion cause great damage. Thus, the emergence of new solutions is important for problems that are solved by conventional methods, but are not so effectively. In this context, the high-speed laser cladding process (HSLC) emerges as a highly efficient alternative to increase the life of components through the deposition of thin layers to improve wear and corrosion resistance. The main objective of this work is to present a systematic review of the HSLC process. The main application areas and features of the process are discussed in detail. Some comparisons with the laser cladding process (LC) are detailed to show the benefits that the HSLC process has over LC. Since scanning speed is one of the main parameters of the HSLC process, the effect of this parameter on microstructure, and mechanical, wear, and corrosion properties is discussed in detail from the information found in the literature. From this review, it is possible to conclude that the HSLC process has great potential to be used in different applications, offering high productivity and efficiency.

© The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2024.The aeronautical industry widely uses the riveting process for metallic sheet metal structure joining processes, mainly when manufactured using aluminum alloys. During riveting operations, some level of geometrical deformation is induced in the airframe structure and such an effect may impact the manufacturing cycle and the product shape. It is important to identify the induced-deformation mechanisms associated with such phenomena and simulation methods capable of foreseeing them numerically or algebraically. The development of simulation methods, even if approximated methodologies, is necessary to assess possible geometrical variations in riveted airframes. Those structures are usually part of wing and fuselage panels. This work presents a general literature review of the riveting process and current modeling techniques aiming to identify modeling methods that could become an adequate baseline approach for riveting-induced deformations. Riveted geometry distortions may produce undesired consequences on manufacturing cycles, aerodynamics performance, and structural efficiency.

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.To perform maneuvers in a fly-by-wire aircraft, a pilot usually commands the yoke or the stick. This command is interpreted by a Flight control computer (FCC), which activates actuators of the control surfaces. To roll large aircraft, it is usual to employ ailerons and roll spoilers as control surfaces. The amount of deflection shared with each control surface is known as control allocation, and it is computed by flight control laws, algorithms embedded in the FCC. This work compares two methods of control allocation to roll aircraft, taking advantage of the flexibility given by fly-by-wire architecture, to compute adequate deflections of ailerons and roll spoilers that comply with requirements of performance, stability and handling qualities. Moreover, it presents alternatives to deal with possible nonlinearities of the roll spoilers. As a first method, it was considered a dead zone for roll spoilers, such that roll spoilers deflect only after certain deflection of ailerons. As a second method, it was considered that ailerons and roll spoilers work together whenever required. The study of the two methods covers real aspects for design in the whole flight envelope, in order to implement in a FCC: study of the bare-airframe (large-heavy transport/cargo aircraft adopted in this case), definition of objectives, control architecture, linear design, nonlinear integration and pilot-in-the-loop simulations. As result, pros and cons of each method are presented. In one hand, the first method is a conservative approach to deal with nonlinear behavior of roll spoilers around small deflections for example but can expose ailerons to rate saturation when deflecting alone in scenarios with poor control power. On the other hand, the second method alleviates the work of the ailerons, but it assumes a reliable model for design, which might be hard to develop. The results were validated with offline simulations and with pilots in a flight simulator.

© 2024, Departamento de Ciencia e Tecnologia Aeroespacial. All rights reserved.The aerospace industry continually seeks to optimize product development processes to remain competitive. Design for Excellence (DFX) plays a crucial role in meeting customer expectations while aligning with organizational capabilities. However, the diversity of DFX technological areas and methods can make it challenging for companies to select the appropriate ones for each project. Successful DFX application, ensuring projects stay within scope, time, cost, and quality constraints without overburdening the development process, often depends on the engineering team’s experience and the project phase. This work maps DFX technological areas to address the decision-making problem of selecting the most suitable ones for various projects. The objective is to evaluate, from the engineering team’s perspective, whether a general approach can guide project managers in selecting key DFX areas, considering a typical aerospace organization’s project portfolio and specific project phase characteristics. Starting with a literature review of DFX in aerospace, the research includes a survey along with senior product development engineers. Quantitative results are gathered using the Likert scale and analyzed through the analytic hierarchy process (AHP). The paper presents a method to guide the initial selection of DFX areas, aiding project managers and engineers in designing complex products.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.In numerous industries, the execution of high-rise tasks necessitates robots equipped with climbing capabilities to reduce human risk exposure (HRE) and meet Environmental, Social, and Governance (ESG) metrics. In response to these demands and drawing inspiration from the climbing behavior observed in animals like inchworms, we have designed an innovative inchworm-like robot. Featuring a 6-degree-of-freedom (DOF) configuration and permanent magnetic adhesion feet, the robot’s adhesion is enhanced by the ability to toggle the magnets on and off through magnetic pack rotation. This versatile design enables the robot not only to ascend various surfaces but also to dynamically adjust its working plane-a crucial advantage for navigating tubular environments and scaling truss structures.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.This study explores the development of a climbing robot for offshore applications with a focus on mitigating human risk exposure (HRE) and Environmental, Social, and Governance (ESG) metrics. Heavy tools are required during maintenance work, thus technical challenges related to surface adaptation, adhesion, locomotion, powertrain and control systems are accomplished. The proposed climbing robot is subjected to a field test and its overall performance proves the potential to improve safety, efficiency and environmental sustainability.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.The primary purpose of climber robots is to undertake tasks that may be hazardous for humans working at height and in hard-to-reach spaces. They improve safety as well as enhance task efficiency and decrease labor costs. Climber robots have been extensively used for activities such as bridge inspection, high-rise building cleaning, fruit picking, high-altitude rescue and military reconnaissance. This paper reviews a list of 51 articles published in the field of mobile robotics and climbing robots in the last five years, mainly related to onshore and offshore oil and gas applications. From the generation of this list, a trend analysis has been performed, where the observed result allowed the perception that the reduction of human exposure to risk (HRE), as well as the ESG principles direct and motivate robotic implementations in this area.

© 2024 IEEE.This article presents the virtual commissioning of a multi-user cyber-physical laboratory for remote access (Multicyber) integrated with Industry 4.0 technologies to promote neoindustrialization. The project incorporates Digital Twins, Virtual and Augmented Reality, Artificial Intelligence, Industrial Robotics, Vision Systems, Autonomous and Collaborative Robots, Cybersecurity, and the Industrial Internet of Things. The objective of the Multicyber project is to create a demonstration center focused on advancing applied research in manufacturing processes. The laboratory features a manufacturing cell with an Autonomous Mobile Robot (AMR), a collaborative anthropomorphic manipulator (cobot), quality inspection via computer vision, a five-axis machine, and a robotic arm for machining. This study presents the simulation of three complete manufacturing routines. Plant Simulation software was used to obtain travel times for the AMR, inspection, and part removal stages, while NX software was used for detailed machining simulations with precision adjustments. The results highlight the benefits of using robotic arms in manufacturing and demonstrate how AMRs and cobots can add value through the planning and integration of routines.

© 2024 IEEE.This paper explores the integration of virtual reality (VR) with teleoperation systems to enhance human-robot interaction. With the rise of remote operations, traditional methods often rely on two-dimensional interfaces, making it challenging to control robots in complex three-dimensional environments. This research presents a VR teleoperation system using the Meta Quest 2 headset, enabling immersive control of a climbing robot with six degrees-of-freedom and magnetic adhesion. The system architecture integrates Unity for virtual simulation and the Robot Operating System (ROS) for real-time communication and control. A virtual environment allows the user to control the virtual robot model through the VR headset and controllers, with ROS serving as the communication bridge between the virtual and physical robots, enabling effective operations in various applications, including high-risk environments (A video is available at https://youtu.be/MiZDOV4IfLA).

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.We use characteristics inspired by the human gait to reduce the energy expenditure of walking in low-cost humanoid robots. Our contribution is to implement the height variation of the center of mass during gait with foot motion around the ankle during gait phase changes. The robot’s foot is curved with a geometric shape that favors rolling motion on the ground. For the control, we extend the Preview Control of Zero-Moment Point technique for the planning of the center of mass, and we will adapt the 3D Linear Inverted Pendulum Model (3D-LIPM) so that our system is linear time-varying. Finally, the inverse kinematics gives us the position of the joints. To measure the energy, we will use a realistic simulator. In the simulator, the fully actuated robot stays in balance in a three-dimensional environment with gravity while walking. The results proved satisfactory, reducing energy expenditure by almost 25% when we combine height-varying and curved feet.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.The use of sub-scales to study flight dynamics is an area that can provide excellent results. With the development of electronics, free flight tests to obtain flight dynamics data on sub-scale aircraft have become increasingly attractive. This paper presents the development of a sub-scale aircraft following the Froude number scaling technique used to achieve representativeness in flight dynamics.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.This article expands upon the analysis conducted in a flight campaign involving a flexible wing UAV with a 4m wingspan and an aspect ratio of 18.9, powered by electric propulsion. The UAV is equipped with a data acquisition system designed to explore the effects of flexibility. The initial phase of the campaign involved flight evaluations aimed at assessing the behavior of the system, particularly in terms of data acquisition. Data compatibility tests were examined using the Flight Path Reconstruction (FPR) technique and the Output Error Method (OEM). The outcomes of the FPR analysis indicate the consistency of the recorded data. The evaluation of biases, scale factors, and time delays using the FPR method successfully established correlations between the recorded data, with notable exceptions in the case of airspeed and angle of attack, which exhibited discrepancies in fitting with classic rigid body kinematics. In this work, the longitudinal FPR using OEM is augmented by incorporating the flexible aircraft dynamic model to provide a more accurate representation of the aircraft, accounting for flexibility effects. In the execution of the FPR, the state variables of the aircraft model, obtained by the integration of the kinematic expression and sensor-gathered data, were expanded by the addition of the structural dynamics. This modification has enabled the computation of α and β values at the vane positions, accounting for structural dynamics effects, and also evaluating accelerations at the wingtips. Synthetic data obtained from an aircraft simulation model were used to evaluate the FPR for the flexible aircraft, and the results have shown that this method can lead to good results when the aircraft model is available. The rigid and flexible FPR were applied to flight-recorded data, and the results obtained with the flexible FPR have not led to enhancements as seen in the simulated data, which indicates that further refinements must be made in the experimental procedures, and evaluations on the structural model and aircraft sensors must be conducted. In conclusion, the method can be used to evaluate additional information beyond the classic FPR developed solely relying on general rigid body kinematics.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.With the development of electronics and programming in recent years, the possibility of aeronautical projects is being studied by academia and industry, with the aim of improving and adapting them to different projects for new applications and realities. One of these cases is the adaptation of projects such as the ground effect vehicles developed by the Soviet Union during the Cold War. This is an aircraft capable of flying close to the surface of the water and whose advantage is the energy saving of the propulsion of up to 40%. There are several companies developing projects of this type around the world, adapting them to the capacity and operating conditions of the different realities. In Brazil, the startup Aeroriver is developing a ground effect vehicle, the Volitan. This project aims to improve the transportation of people and cargo on the rivers of the Amazon. For the project to be successful, it is necessary to know up to what altitude this aircraft can fly to demonstrate energy savings, safety and maneuverability. A sub-scale prototype has been developed for initial testing and is currently being tested to determine the range and flight efficiency improvement of the Volitan in ground effect. Propulsion is provided by electric motors and power is supplied by a battery bank, allowing 15 minutes of flight autonomy. In this paper, the development of the electronics and instrumentation of a prototype is presented. In order to measure the efficiency of Volitan in flight, it will be equipped with load cells to measure the thrust force, RPM, the voltage and current consumed by the motors. Lidar to precisely measure the altitude in relation to the water, and a PixHawk controller used to record accelerations, speeds, position, attitude of the aircraft, etc. As results are presented the energy consumption of the batteries as a function of altitude, in flight condition in ground effect, as well as the thrust force generated by the motors, in addition to determining up to which altitude that the ground effect has a good performance and improves the efficiency of energy consumption of the Volitan.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work proposes an assessment of the delta wing sweep variation of a Generic Future Fighter in the conceptual design phase. Combat aircraft have critical control and therefore the stability analysis of these configurations is compared. Little variation in stability was observed between the 5 different configurations. This indicates that other requirements may become more relevant when designing a fighter aircraft, such as stealth and performance. Thus, this work aims to evaluate the impact of wing sweep on the longitudinal stability of fighter aircraft, considering five different sweep angles: 45°, 47°, 50°, 55°, and 60°. To conduct this analysis, a numerical evaluation, using the Vortex Lattice Method (VLM), wind tunnel results and parameter identification data from past work will be used to obtain the aerodynamic data for each configuration. The aerodynamic data will then be used in a time-domain flight simulation model to analyze the longitudinal stability of the aircraft.

© 2024, Academia Brasileira de Ciencias. All rights reserved.Multirotors Aerial Vehicles are special class of Unmanned Aerial Vehicles with many practical applications. The growing demand for this class of aircraft requires tools that speed up their development. Simulated environments have gained increasing importance, as they facilitate testing and prototyping solutions, where virtual environments allow real-time interaction with simulated models, with similar behavior to real systems. More recently, the use of Augmented Reality has allowed an increasing experience of immersion and integration between the virtual world and a real scenario. This work proposes the use of Augmented Reality technology and a simulated model of a multirotor to create an interactive flight environment, aiming to improve the user experience in the analysis of simulated models. For this purpose, a smartphone was adopted as a hardware platform, a game engine is used as a basis for the development of the Augmented Reality application, that represents a numerical simulation of the flight dynamics and the control system of a multirotor, and a game controller is adopted for user interaction. The resulting system demonstrates that Augmented Reality is a viable technology that can be used to increase the possibilities of evaluating simulated systems.

© 2024 Elsevier LtdPlug and Abandonment (P&A) procedures are mandatory in the oil and gas industry. Conventional well-plugging methods typically involve the laborious and expensive process of cementing, requiring the removal of production tubing. In response to this challenge, a novel approach, known as Thermal Plug and Abandonment (TP&A), has been explored. TP&A proposes the introduction of an exothermic chemical reaction through the production tubing, generating substantial heat to melt the tubing intentionally. The passage formed by the melting process facilitates the traditional insertion of cement, eliminating the need for tubing removal. In this study, the TP&A process is investigated through numerical computations. The oil well structure is approximated as a two-dimensional axisymmetric domain with multiple layers representing different wellbore materials. A numerical code, incorporating chemical kinetics, phase change, and conjugate heat transfer models, was developed in the OpenFOAM® software. The thermite reaction is modeled using a zero-order kinetic model, and the phase change model employs the well-established enthalpy-porosity method to track material melting and solidification. The study primarily focuses on evaluating heat diffusion through the oil well structure during the TP&A process, with a central emphasis on investigating the melting of the production tubing. It was observed that compacting the mixture and diluting it with alumina up to a certain threshold enhanced the tubing's melting. Reducing the initial mixture porosity from 0.55 to 0.4 has increased the tubing's melting volume, constrained to the thermite height, from 60 to approximately 91%. Moreover, this study examined how diluting the thermite mixture with inert alumina affects the heat transfer and, consequently, the tubing's melting. The findings indicated that a 20% dilution can enhance the tubing's melting volume by up to 87%.

© 2024 Elsevier LtdThermite is a powerful energetic material that has potential application in the plug and abandonment (P&A) process of wellbores. The solution named Thermal P&A has withdrawn attention of oil and gas operators all around the world as a prominent method to decrease costs and increase efficiency. Like any technology in its early developments, virtual simulations are effective to predict its viability. However, thermite reactions take place through a complex heterogeneous mechanism that may compromise computational modeling in the P&A scenario. Therefore, this study aims to present a practicable and valid method of computing the 2Al-Fe2O3 thermite reaction propagation in a macroscopic system. The modeled domain consists of a stainless-steel tube filled with the thermite mixture and described in cylindrical coordinates. The energy and species conservation equations are discretized and solved by finite difference methods assuming a constant kinetics rate. A disruption model is adopted to account for heat losses at aluminum vaporization. The numerical results are validated by experimental tests carried out in the same system. Numerical temperature profiles at the tube external surface replicated the experimental data obtained via thermocouples. Effects of tube radius and thermite porosity was investigated. The results showed that decreasing the thermite porosity would be more effective to melt the tube than increasing the internal radius.

© 2023A new hybrid method for transient heat conduction problems is developed and applied to simulate a Plug and Abandonment (P&A) operation of oil wells. An oil well is approximated by concentric disks in a one-dimensional configuration, which allows for use of polar coordinates. The application of the Separation of Variables Method (SVM) is used as the analytical framework for the solution of the conductive heat transfer arising from a volumetric heat source located in the center of the disks. The SVM is able to solve only time-independent boundary conditions. However, using the Duhamel's theorem, the solution determined with the SVM can be used to achieve the solution when both time-dependent boundary conditions and internal heat generation are prescribed. Lastly, for verification purposes, a commercial software that solves the transient temperature field by means of numerical procedures, providing reliability to the analytical method proposed in this work.

© 2024 Elsevier LtdThermite has been considered as a potential alternative for the wellbore plug and abandonment process. This new technology, thermal P&A, may substitute cementation as a cheaper and more compelling material. In this way, different thermite systems and additives are being explored in this scenario. The present study aims to examine the effects of diluting the Fe2O3–2Al thermite system with alumina in search of a more controlled reaction by observing effects on total ejected mass, burning velocity, and temperature levels. Small-scale experiments were conducted where stainless-steel tubes were filled with the thermite system. Thermocouples welded to the tube's external surface allowed us to obtain the temperature profiles at different positions and the overall reaction propagation velocity. The 20 % diluted system suppressed the measured peak temperature, burning rate, and expelled mass of about 10%, 60%, and 45%, respectively, compared to a non-diluted system. Simplified numerical simulation assuming a zero-order kinetics mechanism presented consistent results with the experimental peak temperatures at most positions analyzed. The simulation revealed that the diluted system would not reach the aluminum vaporization temperature as observed in the non-diluted system. Still, instead, it would be limited to the alumina melting temperature of 2327 K. In summary, the diluted system showed substantial reductions in peak temperature, burning rate, and expelled mass, indicating potential cost-effective and controlled applications in Thermal P&A processes.

© 2023 Elsevier B.V.The use of thermite in the plug and abandonment of wellbores is a promising new method for sealing oil wells. However, the reactants for thermite mixtures are usually in a powder state at ambient conditions, making a perfect homogenization for high heat release a challenging task. In this sense, this study aims to investigate the Fe2O3–Al thermite system prepared through a solvent-based method to maximize homogenization of the mixture and enhance energy release during the exothermic reaction. Tests were conducted to compare the burning velocity, ejected mass percentage, and temperature profiles of the reaction through small steel-tubes, comparing a dry-mixed, stoichiometric composition with a solvent-based mixture. The effect of additives such as Al2O3 and Al were also evaluated. Results showed that the solvent-based process led to higher compactness, higher temperatures on the steel tube's exterior, a more stable reaction, and a 40% decrease in ejected material. Also, Al-rich mixtures had faster reactions, lower temperatures, and more ejected material when compared to the stoichiometric system, while Al2O3-diluted mixtures showed a linear decrease in burning velocity and mass ejection at higher dilution levels, with no significant variation in temperature levels. Mixtures with 40% or higher dilution did not self-propagate. Therefore, a thermite mixture prepared using solvent and diluted with Al2O3 at 20–30% is recommended for the thermal plug and abandonment technology.

© 2023 Elsevier B.V.After the end of productive life of a geological oil reservoir, a set of operations for well Plug and Abandonment (P&A) is performed to recover the soil layers to its natural state. As traditional P&A techniques are expensive activities, alternative technologies are gaining renewed interest for capital expenditure reduction and leak risks mitigation. Hence, the Thermal Plug and Abandonment (TP&A) procedure is here investigated by focusing on the fulfillment of two intermediate milestones, combining new technology with conventional P&A practices. The first milestone consists in applying a thermite exothermic reaction to generate enough heat for melting the entire thickness of the production tube. The second milestone aims to determine if the resulting molten section has sufficient dimensions to allow for the passage of the cement pumped downhole, thus ensuring the complete sealing of the oil well's cross-section. The thermal investigation was conducted by applying a homogenized form of the Finite Integral Transform (FIT) analytical framework to solve the transient heat conduction equation in 2-D polar coordinates. The well assembly was geometrically discretized as a multilayered circular domain. The thermite reaction was modeled as a theoretical volumetric heat source profile dependent on both time and space, placed in the innermost layer. While a pure FIT approach may only be used to solve Neumann boundary conditions, the combined scheme applied here copes with any type of boundary condition. Hence, the integration of FIT with homogenization satisfies the Dirichlet condition requirement of the TP&A procedure. The methodology was verified through an equivalent Finite Volume Method (FVM) solution obtained using a commercial code. The results evidenced that within the 5 min duration of thermite reaction, the entire circumferential section of the production tube exceeds the steel melting temperature by at least 227 °C, thus fulfilling both milestones set. The research outcomes are part of a series of investigation steps to thoroughly analyze the new TP&A technology with regard to its compliance with the regulatory norms established to P&A operations.

© 2023 Elsevier Masson SASWhen a well does not fulfil its objectives, it is repurposed or permanently plugged, a shift in budget from revenue to Plug and Abandonment (P&A) expenditures occurs. New technologies being developed for P&A make use of a powerful heat emitter for melting the surrounding of the well forming a solid plug after the cool down. However, there is a gap in understanding the heat transport process in the well and much need for appropriate mathematical tools and solutions for estimating the effectiveness of Thermal P&A. The thermal analysis of the process requires eigenvalues in polar coordinates, which return only real quantities due to its implicitly dependence on the angular eigenvalues. Here, a hybrid analytical/numerical method is applied to an asymmetric transient heat conduction problem. The oil well is conceived as a 2-D multi-layer disc cast in polar coordinates, where the Separation of Variables Method (SVM) was applied to achieve a closed-form solution. Asymmetric boundary conditions of first, second and third kind can be implemented utilizing the proposed framework. A Finite Volume Method (FVM) numerical solution was produced for code verification. Lastly, research results show that temperature levels arising from the thermite reaction throughout the composite cylinder domain in radial and azimuthal ranges are enough for surpassing the melting point of the production tube steel. The results evidenced the thermal efficiency of the TP&A procedure and suggested that the production column may be destroyed by fusion, thus reducing tamponing expenses significantly.

© 2023 Elsevier LtdThe end of the production phase of an offshore oil well represents a remarkable shift in field operations from extraction to plug and abandonment. The international normative requirements for permanent well plugging demand a series of technical maneuvers to avoid structural failures and the formation of leakage paths during or after the sealing process. The current closure technique requires a complete or partial removal of the production column before the borehole may be plugged with Portland cement. However, the tube removal process frequently results in an increase in the involved time and costs. Hence, the current research was aimed at investigating the prototype approach of Thermal Plug and Abandonment of wells by applying a thermite heat emitter device to melt the production column's steel. Here, the Finite Integral Transform analytical method was computationally implemented through an inhouse code to calculate the resultant transient temperature fields at the multilayered medium. The results were compared to a Finite Volume Method numerical solution to enhance the study's reliability. The research outcomes provided insight that even in the event of a partial thermite reaction failure and a highly nonuniform heat pattern, the resultant molten azimuthal length of the production column may still allow enough room for cement flow. It was estimated through the temperatures achieved that the heat emitter is capable of melting at least nearly three-quarters of the production tube's azimuthal length, thus eliminating the need for its removal and significantly reducing the sealing process operational costs.

Copyright © 2024 by ASME.This article proposes a new formulation for a phase change model based on the enthalpy-porosity idea. A general one-energy equation model (1EEM) is extended to deal with the melting and solidification of pure substances and alloys. Before melting and after solidification, solid material is seen as a porous media with low porosity and very small permeability. During phase change, thermal equilibrium in the mushy zone is assumed. Viscous and form drag in the volume-Averaged momentum equation are reduced as the temperature rises above the melting point. In the energy equation, latent heat is treated implicitly in the accumulation term instead of explicitly as in most works in the literature. Liquid fraction for the entire field is updated after a new temperature field is calculated. Thermophysical properties are updated with the new liquid fraction field. Governing equations are discretized according to the control-volume method. Algebraic equation sets are relaxed with the Simple Method. Inner iterations make use of the Strong Implicit Procedure. Preliminary results indicate good agreement with the literature for pure substances.

© 2024 by Begell House, Inc.The thermite reaction is a self-sustained exothermic reaction commonly employed in welding processes of railway tracks, material synthesis, pyrotechnics, etc. More recently, this reaction has been assessed to plug depleted oil wells. The investigated geometry is modeled as a two-dimensional axisymmetric domain with a thermite mixture compressed between a polymethylmethacrylate (PMMA) lid and a stainless steel disk. First-order kinetic is assumed for the chemical kinetics model. The governing equations are discretized with the finite-volume approach. Experimental validation is performed by comparing numerical combustion velocities and peak temperatures with the experimental data in the literature. The results demonstrate a remarkable thermal gradient through the longitudinal direction, displaying higher thermal losses next to the thermite-steel interface. These heat losses also affect the melting of species, as a small portion of alumina remains entirely solid during the reaction.

© 2024 The AuthorsThe demand to capture translaminar crack growth under fatigue loading scenarios led this work contribution to carry out the Finite Fracture Mechanics (FFM) method in fatigue damage growth and the application of the Paris model to generate the translaminar damage propagation prediction. The purpose of this study is to analyse the effect of fibre orientation on translaminar crack propagation rate using the FFM model, which includes cycle damage increment estimation and fractographic analysis. The results confirm the feasibility of FFM in predicting crack growth and estimating life under cyclic loading. However, C-scan analysis and the revised crack propagation direction are critical in determining the realistic crack length, considering adhesive failure along the fibre direction. Additionally, this work contribution is also related to the application of the Paris model (based on dL/dN vs ΔK) to generate the translaminar damage propagation prediction model. The most dominant damage mechanism was the splitting pattern, which changed the aspect of failure for each laminate architecture as a function of fibre orientation. The laminate with multidirectional fibre orientation exhibited higher resistance to translaminar crack propagation due to the growth of splitting and delamination in multiple directions. The fibre orientation changed the propagation path, which influenced the fracture toughness and crack propagation rate behaviour.

© 2024, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.Thermoplastic composites offer advantages over thermoset composites, such as welding, which allows for complex geometries and eliminates drawbacks of mechanical fastening and adhesive bonding. Most thermoplastic resistance welding studies rely on experiments, and reliable models are needed for wider applications. In this paper, a numerical model for the thermoplastic welding process is proposed. The model is based on one-dimensional temperature distribution around the joint interface obtained from the transient heat conduction equation. To evaluate the bond strength, a bonding model that considers intimate contact and autohesion was used. The material and the thermal properties as well as the processing parameters were obtained from the literature. Eight modeling conditions were investigated, and the results were discussed. The model proved useful for conducting parametric studies, which can assist in the selection of processing parameters for future experimental tests. It provided an overview of the temporal evolution of the intimate contact, autohesion, and degree of bonding mechanisms along the weld thickness under various modeling conditions for the APC-2/PEEK composite.

© 2024 The AuthorsThe demand to capture translaminar crack growth under fatigue loading scenarios led this work contribution to carry out the Finite Fracture Mechanics (FFM) method in fatigue damage growth and the application of the Paris model to generate the translaminar damage propagation prediction. The purpose of this study is to analyse the effect of fibre orientation on translaminar crack propagation rate using the FFM model, which includes cycle damage increment estimation and fractographic analysis. The results confirm the feasibility of FFM in predicting crack growth and estimating life under cyclic loading. However, C-scan analysis and the revised crack propagation direction are critical in determining the realistic crack length, considering adhesive failure along the fibre direction. Additionally, this work contribution is also related to the application of the Paris model (based on dL/dN vs ΔK) to generate the translaminar damage propagation prediction model. The most dominant damage mechanism was the splitting pattern, which changed the aspect of failure for each laminate architecture as a function of fibre orientation. The laminate with multidirectional fibre orientation exhibited higher resistance to translaminar crack propagation due to the growth of splitting and delamination in multiple directions. The fibre orientation changed the propagation path, which influenced the fracture toughness and crack propagation rate behaviour.

© 2024, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.Thermoplastic composites offer advantages over thermoset composites, such as welding, which allows for complex geometries and eliminates drawbacks of mechanical fastening and adhesive bonding. Most thermoplastic resistance welding studies rely on experiments, and reliable models are needed for wider applications. In this paper, a numerical model for the thermoplastic welding process is proposed. The model is based on one-dimensional temperature distribution around the joint interface obtained from the transient heat conduction equation. To evaluate the bond strength, a bonding model that considers intimate contact and autohesion was used. The material and the thermal properties as well as the processing parameters were obtained from the literature. Eight modeling conditions were investigated, and the results were discussed. The model proved useful for conducting parametric studies, which can assist in the selection of processing parameters for future experimental tests. It provided an overview of the temporal evolution of the intimate contact, autohesion, and degree of bonding mechanisms along the weld thickness under various modeling conditions for the APC-2/PEEK composite.

© 2024, The Author(s), under exclusive license to Springer Nature Switzerland AG.The objective of present paper is to examine the plastic anisotropy behaviour of steel sheet, employing the Barlat´s Yld 2000-2d yield stress criterion and the corresponding non-associated plastic flow rule. New Barlat´s coefficients of anisotropy were defined and calibrated from material experimental data of simple uniaxial tension and equal biaxial stress tests. The new set of coefficients calculated from the experimental Lankford anisotropy coefficients (r-values), normalized yield stress (s-values), equal biaxial stress parameters (rb and σb) were numerically obtained using the Newton-Raphson method. The investigated metal was the highly anisotropic AISI 439 steel sheets found in the literature. In the results analysis and discussion, the new coefficients of anisotropy of the Barlat´s non-associated plastic flow rule were calculated and validated by plotting on the same graph the predicted r-value and s-value curves and the experimental data for the anisotropic steel sheets. The correlations have revealed that the Barlat´s yield criterion and the plastic flow stress potential were not coincident. Furthermore, the predicted limit strain curve of 439 steel correlated better with the experimental FLCTD transverse curve when using the shear stress fracture criterion and the non-associated plastic potential than the associated flow rule. Therefore, the Barlat´s Yld 2000-2d non-associated plastic flow rule provides a better fit with the experimental Lankford and equal biaxial coefficients of anisotropy and the FLCTD curve results of AISI 439 steel sheets.

© 2024 International Forum on Aeroelasticity and Structural Dynamics, IFASD 2024. All rights reserved.The present work reports on the development of a numerical aerothermoelastic tool that accounts for nonlinearities of multi-physical sources to investigate the behavior of flexible wings made of a hybrid smart material. Here, hybrid materials consist of laminated composites reinforced with embedded shape memory alloy wires. The proposed model gathers geometrical, material, and aerodynamic nonlinearities to the thermal heating dynamics of SMA wires via the Joule effect. To this end, a geometrically nonlinear FE beam model is coupled with material nonlinearities via a micromechanical model that computes the homogenized properties of hybrid laminates. Nonlinear aerodynamic effects are introduced through an unsteady strip theory method in the time domain, along with the assumption of follower aerodynamic forces and a quasi-steady stall model. A set of aerothermoelastic cases was simulated by assuming various layups and SMA temperatures to tailor and analyze the aeroelastic response of hybrid wings. The outcomes have shown a considerable reduction in post-flutter oscillations as the SMA temperature increases, indicating evidence of the capability of hybrid materials for aeroelastic applications.

© 2024 International Forum on Aeroelasticity and Structural Dynamics, IFASD 2024. All rights reserved.Future aerial mobility will likely be powered by propeller propulsion, as it is more suitable for use in combination with electric motors. Therefore avoiding rotor instabilities becomes a major concern in the early project phases for the next generation of aircraft. Within this context, this work focuses on the application of Shape Memory Alloys (SMA) for Whirl Flutter (WF) suppression in propeller-driven aircraft. SMAs have a thermal-dependent modulus of elasticity, which allows the use of this class of materials to locally control the stiffness of the connections between the motor and the wing. For most of the flight, the mounting stiffness could be maintained at a minimum to better isolate the vibration coming from the motor, and only at high speeds it could be increased to avoid aeroelastic instabilities. To conduct the study, a 4 degree of freedom (dof) model of a wing section with an installed rotor was implemented and verified. This model combines a typical aeroelastic section, with springs associated with pitch and plunge dof, and the classical rotor model used in WF studies, which idealizes the rotor mounting by two torsion springs associated with pitch and yaw dof. Predictions obtained using the proposed model were compared with previous results from the literature. Following the model verification, the application of SMA was implemented by assuming that the connecting stiffness associated with the rotor installation is dependent on temperature, simulating an SMA-made mounting. Thus, it was possible to map the final flutter velocity of the system as a function of the temperatures associated with the rotor installation. The obtained results demonstrate that the flutter speed of the system may be significantly modified using this approach. They also indicate that the control of the SMA temperature shifts the dominant flutter mechanism from WF to the classical wing flutter, increasing even more the flutter speed of the system.

© The Author(s) 2023.Abstract: An adjoint-based method is presented for determining manufacturing tolerances for aerodynamic surfaces with natural laminar flow subjected to wavy excrescences. The growth of convective unstable disturbances is computed by solving Euler, boundary layer, and parabolized stability equations. The gradient of the kinetic energy of disturbances in the boundary layer (E) with respect to surface grid points is calculated by solving adjoints of the governing equations. The accuracy of approximations of ΔE, using gradients obtained from adjoint, is investigated for several waviness heights. It is also shown how second-order derivatives increase the accuracy of approximations of ΔE when surface deformations are large. Then, for specific flight conditions, using the steepest ascent and the sequential least squares programming methodologies, the waviness profile with minimum L2-norm that causes a specific increase in the maximum value of N- factor, ΔN, is found. Finally, numerical tests are performed using the NLF(2)-0415 airfoil to specify tolerance levels for ΔN up to 2.0 for different flight conditions. Most simulations are carried out for a Mach number and angle of attack equal to 0.5 and 1.25∘, respectively, and with Reynolds numbers between 9×106 and 15×106 and for waviness profiles with different ranges of wavelengths. Finally, some additional studies are presented for different angles of attack and Mach numbers to show their effects on the computed tolerances. Graphic abstract: (Figure presented.).

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This manuscript discusses the impacts of two factors on the results of a non-viscous CFD simulation of a combat aircraft: mesh refinement and the leading-edge sweep angle. Unlike viscous simulations, the non-viscous simulation of a delta wing with a rounded leading edge has a unique characteristic where mesh refinement consistently alters the flow topology, making mesh independence analysis ambiguous. To investigate this phenomenon further, the Generic Future Fighter, an aircraft initially devised by Linköping University and further studied in conjunction with Instituto Tecnológico de Aeronáutica, was used to validate this issue through aerodynamic coefficients obtained from wind tunnel tests from another work. Subsequently, using the mesh that yielded the most accurate results, the leading-edge sweep angle was varied while keeping the rest of the aircraft and other wing geometric parameters constant. The results of the first phase confirmed that mesh refinement progressively delays the separation of the leading-edge vortex. The results of the second phase were inconclusive, highlighting several points that require further investigation. The manuscript also presents a discussion on the highly nonlinear interaction between the canard vortex and the wing vortex, as well as the effect of the mesh on these interactions, an aspect lacking in recent studies which typically consider only a single lifting surface.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The topological optimization of airfoils and wings is a highly multidisciplinary problem which often depends on industry knowledge and qualitative dialogue with areas other than aerodynamics to produce viable results. Additionally, certain numerical issues, mostly due to the high dimensionality of the optimization problems involved, persist in spite of recent advancements in Aerodynamic Shape Optimization applications. To avoid these issues, a fully data-driven process for geometry proposals and aerodynamic coefficient predictions was developed. An Adversarial Autoencoder is trained to replicate the geometries of subsonic airfoils by encoding them to a latent space of low dimensionality. Using design variables in said space, the geometry can be optimized for the aerodynamic predictions of a surrogate model combining semi-empirical evaluations of drag and lift with neural networks trained on XFOIL data. The result is a fast, fully data-driven airfoil design process capable of producing geometries coherent with multidisciplinary demands and similar historical wing profiles.

© 2021 SAE International.High and ultra-high pressure direct injection (UHPDI) can enhance efficiency gains with flex-fuel engines operating on ethanol, gasoline, or their mixtures. This application aims to increase the engine's compression ratio (CR), which uses low CR for gasoline due to the knocking phenomenon. This type of technology, involving injection pressures above 1000 bar, permits late fuel injection during the compression phase, preventing auto-ignition and allowing for higher compression ratios. UHPDI generates a highly turbulent spray with significant momentum, improving air-fuel mix preparation, and combustion, resulting in even greater benefits while minimizing particulate matter emissions. This study aims to develop ultra-high-pressure injection systems using gasoline RON95 and hydrated ethanol in a single-cylinder engine with optical access. Experimental tests will be conducted in an optically accessible spark ignition research engine, employing thermodynamic, optical, and emission results. In the present work, the spark plug was placed in the lateral, so the ignition and part of the flame propagate close to the cylinder wall, and it will exchange with greater heat to the wall than the flame portions that propagate towards the central region of the chamber. Therefore, the flame front propagates at different speeds; causing stretching and wrinkling that can lead to instabilities and cyclic variability. To address this issue, this work presents experimental results that, through the images post-processing of flames under a SOI (start of injection) sweep strategy in the compression phase to closer of the spark ignition, associating the non-uniform propagation velocity of the flame with the cyclic variability. The fuel impingement on the wall was critical in this scenario, which led to higher soot concentrations and diffusive flames for gasoline. It was found that the injection close to the spark plug enhances the heat release, and combustion stability, decreasing soot emissions. Total unburned hydrocarbons (THC), Nitrous oxides (NOx), aldehydes, and soot emissions decreased for end of injection events closer to the spark ignition. This trend opposes the increase observed in CO emissions.

© 2021 SAE International.Despite the increasing electrification of current vehicles, Diesel engines will continue to be used for several decades to come. There is still a need to introduce emission control technologies, especially those that show good potential and do not require extensive engine modifications. The increasing focus on reducing pollutant emissions and improving energy efficiency has prompted engine manufacturers to continuously strive for technological progress. The aim is to ensure compliance with environmental regulations and the fulfillment of social expectations. Specifically, new Diesel engine projects face the challenge of minimizing both nitrogen oxides (NOx) and soot emissions, which requires significant investiment in research to develop innovative combustion methods and exhaust gas treatment. One of these innovative methods is Ducted Fuel Injection (DFI), which aims to reduce emissions by improving spray development to obtain a better mixture at flame upstream. This study presents an experimental investigation carried out on a test bench with a single-cylinder compression ignition (CI) engine with a compression ratio of 16.5:1, in conjunction with an active alternating current dynamometer. The Diesel engine is equipped with instruments for measuring various parameters, including the pressure in the combustion chamber, the exhaust gas temperature, the temperature and pressure of the intake air, and coolant temperature, to name but a few. The engine was modified to incorporate the concept of Duct Fuel Injection (DFI), where the injected fuel is routed through a duct behind the injector, resulting in a more efficient and homogeneous air/fuel mixture, thus improving combustion. The aim of this study was to vary the engine load from approximately 4.2 to 7.3 bar IMEP. The load variation was achieved by changing the mass of fuel injected during the main injection. The injection timing was constant over the entire load variation range for both main injection and pre-injection. The results obtained from the experiments show that DFI produces a satisfactory reduction in soot formation compared to free spraying (FS). Although a lower cylinder pressure was observed in DFI mode at all loads studied due to of the delayed combustion caused by the presence of the duct, the engine performance was comparable to that of free spray mode.

© 2024 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.Aircraft propulsion electrification is currently being considered by industry and academia as one of the most promising strategies to reduce air transport emissions and increase overall efficiency levels. In the past decade, several papers were published on this subject, with the majority indicating encouraging fuel burn benefits versus conventional, fossil-fuel-based propulsion systems when future technologies, novel aircraft configurations, and synergistic propulsive-airframe integration are employed. However, a much smaller effort has been applied to the economic aspects of hybrid and fully electric propulsion, which are crucial for a successful product introduction. The present paper describes the modeling of a baseline general-aviation-type aircraft and its propulsion system retrofit with electrified architectures, exploring different electrification strategies for a fixed airframe design. Analyses are performed at the aircraft level, comparing recurring and cash operating costs for several cost and durability scenarios. While considerable CO2 reductions may be achieved in some electrification strategies, aircraft performance is significantly penalized, and important improvements in economic figures of merit are needed in order to make electrified propulsion cost-competitive. Electrified architectures tend to increase costs: turboelectric increases recurring equipment costs, while hybrid-electric increases recurring and direct maintenance costs, especially at higher degrees of energy hybridization.

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.Within the current restringing emissions regulations, the trends for renewable fuel adoption, such as ethanol, have grown in the automotive industry. Besides the benefits when used as the single fuel, ethanol can also leverage the advantages in the context of hybrid vehicles by replacing the petroleum derived fuels in such configuration. In this scenario, the optimization of combustion events in internal combustion engines is paramount to not only promote high performance, but also support fuel economy. Factors such as the combustion chamber design, the positioning of the spark plug and the injector are crucial to support a successful flame propagation, avoiding misfires and decreasing knock propensity. In addition, wearing of those parts can jeopardize the occurrence of reliable and stable combustion events leading to poor emission performance, high fuel consumption and potential hardware damages due to occurrence of knocking events. This research aims to numerically analyze the effects of different spark plug electrode gaps in engine-like conditions by applying Star-CD, a computational fluid dynamics commercial software, to mimic different configurations and operational conditions. The validation and tuning of the numerical models are conducted based on experimental tests performed in an optically accessible direct injection spark ignition engine, operating with two ethanol-based fuels, E96W4 and E100. Thermodynamic data were simultaneously acquired and correlated with the digital UV–visible images in cycle-resolved basis. The numerical models adopted consist of 3-Zones Extended Coherent Flame and Imposed Stretch Spark Ignition Models, applied for the modeling of the combustion and the spark plug, respectively.

© 2024 by the authors.The gasification of residues into syngas offers a versatile gaseous fuel that can be used to produce heat and power in various applications. However, the application of syngas in engines presents several challenges due to the changes in its composition. Such variations can significantly alter the optimal operational conditions of the engines that are fueled with syngas, resulting in combustion instability, high engine variability, and misfires. In this context, this work presents an experimental investigation conducted on a port-fuel injection spark-ignition optical research engine using three different syngas mixtures, with a particular focus on the effects of CO/H2 and diluent ratios. A comparative analysis is made against methane, considered as the baseline fuel. The in-cylinder pressure and related parameters are examined as indicators of combustion behavior. Additionally, 2D cycle-resolved digital visualization is employed to trace flame front propagation. Custom image processing techniques are applied to estimate flame speed, displacement, and morphological parameters. The engine runs at a constant speed (900 rpm) and with full throttle like stationary engine applications. The excess air–fuel ratios vary from 1.0 to 1.4 by adjusting the injection time and the spark timing according to the maximum brake torque of the baseline fuel. A thermodynamic analysis revealed notable trends in in-cylinder pressure traces, indicative of differences in combustion evolution and peak pressures among the syngas mixtures and methane. Moreover, the study quantified parameters such as the mass fraction burned, combustion stability (COVIMEP), and fuel conversion efficiency. The analysis provided insights into flame morphology, propagation speed, and distortion under varying conditions, shedding light on the influence of fuel composition and air dilution. Overall, the results contribute to advancing the understanding of syngas combustion behavior in SI engines and hold implications for optimizing engine performance and developing numerical models.

© 2024 Elsevier LtdThe increasing popularity of plug-in hybrid vehicles has prompted investigation of options such as range extender units, which may include small engines powered by biofuels. To minimize energy consumption, the best technologies must be chosen, including the use of exhaust gas recirculation (EGR, as a charge dilution technique) and the best alternative for fuel injection systems. Therefore, a combustion evaluation was conducted on an optically accessible engine fueled with hydrous ethanol to determine the effects of different injection modes, such as direct injection (DI) and port fuel injection (PFI), combined with EGR. The study employed high-speed camera imaging to analyze flame morphological characteristics and understand their impact on in-cylinder thermodynamics and engine emissions. The DI mode presented more stability than PFI, although the dilution limit was lower for DI.

© IMechE 2023.Plug-in hybrid electric vehicles (PHEV) have the potential of combining the benefits of a renewable electric mix with biofuels. More recently, PHEV have been designed to be equipped with a small combustion engine known as range extender (RE), thus allowing an improvement in vehicle’s range while converting fuel energy through a highly efficient path. Despite being a convenient strategy for decarbonizing light vehicles, the intermittent operation of the engine may create issues regarding the catalytic conversion of pollutants, yielding an increase in local harmful emissions. This drawback may be intensified depending on the used fuel. Hydrous ethanol is a promising alternative for gasoline and is already available in some countries, such as Brazil. However, ethanol has a great enthalpy of vaporization and it results in a charge cooling, affecting the catalyst warm-up and making the intermittent operation with ethanol more challenging. Hence, this study was motivated by the need of improving the catalytic efficiency of flexfuel RE operating with both gasoline and hydrous ethanol. Thus, a calibration was firstly performed to shorten the warm-up phase with ethanol. Then, an electrical heater was employed for accelerated catalyst heating, further improving emissions from ethanol operation, aiming at attaining future emissions regulations. Experimental tests were conducted in a vehicle under FTP72 cycle using a chassis dynamometer. The calibration adjustments resulted in a warm-up phase for ethanol <10 s longer than that for gasoline. The stable operation phase resulted in similar emissions for both fuels. On the cycle average, a reduction in CO for ethanol was observed, and although the methane and NOx emissions were slightly increased due to colder catalyst operation, significant improvements were obtained on a well-to-wheel (WTW) analysis. The use of an electrically heated catalyst (EHC) improved the emissions during the warm-up phase, significantly reducing the emission of NOx and non-methane organic compounds.

© 2024 SAE International. All rights reserved.Plug-in hybrid electric vehicles have the potential of combining the benefits of electric vehicle in terms of low emissions and internal combustion engine vehicles in terms of vehicle range. With the addition of a renewable fuel, the CO2 potential reduction increase even more. The last trends for PHEV are small combustion engine known as range extender, with battery package between full hybrid and electric powertrains. Thus, allowing an improvement in vehicle's range, reducing battery materials while converting fuel energy through a highly efficient path. Although these vehicles have been proved to be a convenient strategy for decarbonizing the light vehicles, the use of alternative fuels is poorly studied. In this work, hydrous ethanol is chosen because is already available in some countries, such as USA and Brazil, and have an ultra-low well-to-tank CO2 emission. The study combines experimental and numerical tools for the development of an ultra-efficient and ultra-low emission powertrain in a range extender BMW i3 fueled with hydrous ethanol. Experimental tests were conducted in an engine test bench and a chassis dynamometer under FTP72 emission cycle. The vehicle simulation was performed in AVL Cruise M for the control strategy optimization and vehicle test under different driving conditions. For comparison, the vehicle was also tested with the battery electric version. In summary, this study demonstrates that the utilization of hydrous ethanol as a range-extender fuel in plug-in hybrid electric vehicles can significantly enhance vehicle range while reducing well-to-wheel CO2 emissions. The range-extender configuration, particularly with E100, exhibits promising potential, making it a competitive choice for drivers concerned about range limitations and environmental impact. The research emphasizes the adaptability of hydrous ethanol-fueled PHEVs across various driving scenarios, contributing to the ongoing global initiative to decarbonize light vehicles and combat climate change.

© 2024Producer gas from biomass gasification offers a renewable alternative to fossil fuels. However, its low energy density results in low conversion efficiency in engines. Blending producer gas with higher-ranked fuels such as hydrogen has been proposed to overcome this issue. This study investigates the combustion of artificially made producer gas and hydrogen mixtures in an optical SI engine. The molar fraction of hydrogen in producer gas ranged from 14 to 62%, which simulated additions of hydrogen to a low calorific producer gas. The experiments are conducted at a constant speed and stoichiometric ratio. The spark timing is varied to achieve the highest power for each mixture. Results include data on emissions, thermodynamics, and flame morphology. The molar fraction of 33% hydrogen on producer gas improves the flame morphology of the mixture to resemble that of pure natural gas, while 24–36% was found to be the optimal range for engines initially designed to run on natural gas with lower NOx and UHC emissions.

© 2023 Elsevier LtdOne way to achieve a fast track for the decarbonization of the transportation sector is through the usage of biofuels. Among the many biofuels available for transportation, ethanol is one of the most promising, especially when combined with direct-injection spark-ignited engine technologies. The present work aims to validate 3D Computation Fluid Dynamics (CFD) ethanol spray and combustion models with the calibration of specific model parameters using experimental data obtained with optical measurements. Focus is given on the investigation and determination of the Extended Coherent Flame Model parameters for hydrous ethanol turbulent spray combustion. To characterize the spray produced by the injector, measurements obtained with a Phase Doppler Interferometer system are used. Natural luminosity and in-cylinder pressure are acquired on a single-cylinder research engine with optical access. The work also considers results obtained from 1D and 3D CFD models to supplement the acquired experimental setup. From the comparison between experimental and numerical results, it comes out that a correction of the Extended Coherent Flame Model turbulence stretch parameter can be done according to a ratio of flow and combustion length scales obtained at the spark time. In this sense, an expression is proposed to allow the correction of such a parameter in different engine operating conditions. Accordingly, in-cylinder mean effective pressure calculated with 3D CFD simulations show a good agreement with the experimental data for all studied cases.

© 2024 Elsevier B.V.The mechanical properties of parts built with material extrusion additive manufacturing are highly dependent on the material distribution within parts’ microstructure. This varies with the choice of process parameters. Therefore, when designing a functional printed part, one must tailor the printing parameters in order to obtain the desired properties, such as minimal voids. The present work proposes an optimisation method that designs printing parameters to minimise manufacturing time while keeping the void volume fraction at very low values (hence improving mechanical properties), keeping dimensions within tight tolerances and guaranteeing structural integrity. The new optimisation method utilises the authors’ previously developed software VOLCO-X, which is capable of efficiently predicting material distribution from filament extrusion within printed parts, including print track dimensions and microstructure geometry, without the need for any experimental calibration. In order to validate the proposed optimisation scheme, optimised printed parts using the scheme and parts using printing parameters determined by a commercial slicing software were manufactured and compared for different printing speeds and deposition strategies. At printing speed of 16 mm/s, it was possible to decrease the manufacturing time by more than 20% and structural mass by more than 5% in comparison to the commercial slicer printed part, whilst maintaining similar mechanical properties. At printing speed of 96 mm/s, due to the high printing speed, the commercial printed part presented gap faults between deposited strands, while the optimised part had structural integrity. At this printing speed, the optimised printed part presented significant improvements in terms of mechanical properties. The proposed optimisation methodology, in conjunction with VOLCO-X, is a powerful tool that can be used to improve manufacturing by filament extrusion. This innovative tool allows the identification of printing parameters without experiments and trial-and-error approaches, thus saving time and expense.

© 2024, Academia Brasileira de Ciencias. All rights reserved.Currently, it is crucial for the lubricant formulation industry to explore cost-effective and environmentally friendly methodologies for analyzing the tribological properties of engine aviation lubricants under high-temperature and high-pressure operating conditions. This study demonstrates the feasibility of employing molecular dynamic simulations to gain essential insights into the evolution of the tribological properties of lubricants during operation. A three-layer molecular model was devised, comprising nickel aluminide molecules in the top and bottom layers, and polyol ester in the core. The impact of sliding velocities ranging from 20 km/h to 100 km/h was investigated under varying temperature and pressure conditions. Concentration, temperature and velocity profiles, radial distribution function, mean square displacement, and friction coefficient were calculated and analyzed in detail. Notably, the highest friction coefficients – ranging from 2.5 to 0.75-were observed at the lowest temperature and pressure conditions tested. Conversely, other sections of the gas turbine exhibited substantially lower friction coefficients – ranging from 0 to 0.01.Simulations demonstrate that increasing pressure and temperature reduce polymer chain mobility, leading to stronger internal interactions within the lubricant. Consequently, lubricant adsorption onto metal surfaces decreases. Furthermore, the lubricant performs exceptionally well when its molecules encounter higher velocities and temperatures. Based on the results obtained, the research demonstrates that the presented technique provides both quantitative and qualitative tribological information essential for understanding a system molecular behavior, serving as a guiding framework for researchers in the field.

Copyright ©2024 by the International Astronautical Federation (IAF). All rights reserved.Hypergolic fuels are crucial in the space industry, particularly in satellite propulsion systems, where their ability to ignite spontaneously upon contact is extremely valuable. Among the most established hypergolic propellants are hydrazine and nitrogen tetroxide. However, their high toxicity not only drives up the cost of satellite integration but also poses significant environmental risks. To address these challenges, researchers have been focusing on developing new environmentally friendly hypergolic bipropellants using high-concentration hydrogen peroxide as an oxidizer. This study explores the use of different catalysts in the decomposition of 90% hydrogen peroxide, aiming to propose a new green fuel blend based on n-butanol and monoethanolamine (MEA). The catalyst and the optimized fuel composition were selected in terms of the ignition delay time (IDT) with hydrogen peroxide (90%). Finally, a fuel solution consisting of 31.5% n-butanol, 60% MEA, and 8.5% copper nitrate trihydrate with a minimum IDT of 20 ms was achieved, and a characterization of the green fuel blend was made in terms of viscosity, density, flashpoint, and combustion enthalpy. The findings suggest that n-butanol can serve as an additive to enhance MEA, improving the freezing point, IDT, and viscosity of the hypergolic pair with hydrogen peroxide (90%).

Copyright © 2024 by the International Astronautical Federation (IAF). All rights reserved.Reactive molecular dynamics simulations were utilized to investigate the reaction between ammonium Perchlorate (AP) and aluminum (Al) particles. Two distinct sets of simulations were conducted, one involving a pure aluminum particle and the other featuring a passivated aluminum particle. The aim was to examine and compare the behavior of the reactive systems under different conditions. The simulations were performed using the ReaxFF force field, allowing for a detailed representation of chemical reactions at the atomic scale. Results revealed significant differences in the reaction dynamics between the two systems. The pure aluminum particle exhibited a more rapid and exothermic reaction with AP, leading to a higher release of energy and potentially enhanced propulsion performance. Conversely, the passivated aluminum particle displayed a slower and less exothermic reaction, attributed to the presence of an oxide layer inhibiting direct contact between aluminum and AP molecules. Additionally, kinetic parameters such as reaction rate constants were calculated for both sets of simulations, providing insights into the reaction kinetics of AP-A1 systems. Furthermore, the initial decomposition mechanism of AP was investigated, shedding light on the early stages of the reaction process. These findings provide valuable insights into the role of aluminum passivation in solid rocket propellant formulations and highlight the potential for optimizing energetic materials through molecular-level simulations. Overall, the comprehensive analysis presented in this study advances our understanding of AP-A1 interactions and offers a foundation for further research aimed at enhancing the performance and safety of energetic materials in propulsion applications.

Copyright ©2024 by the International Astronautical Federation (IAF). All rights reserved.Nitramines, like RDX and HMX, are also alternatives to AP as main components in smokeless propellants. They have high specific impulse but are moderately sensitive and have a slightly negative oxygen balance and are therefore unable to contribute positively to the oxygen balance of the propellant. Crystal defects are a constant in applied energetic materials (EMs) and play a crucial role in thermal degradation, combustion and ignition mechanisms, and subsequent aging. Defect engineering is the process of studying how defects affect an EM’s qualities and performances in order to design new EMs that meet the required specifications. An emerging field of study in energetic materials is crystal-defect engineering, which offers previously unheard-of opportunities for regulating physical, chemical, and electrical properties as well as propellants, explosives, and pyrotechnics compositions. There are numerous types of crystal defects, including line defects (dislocation), planar defects (twin, shear band, crack, and surface defect), and volume defects (void). Point defects also include orientational defects and element doping. In this study, ReaxFF molecular dynamics simulations were used to examine the effects of molecule vacancies on the reaction kinetics and thermal decomposition mechanisms of condensed-phase - HMX at different temperatures. The thermal decomposition of HMX is the primary event in the combustion process of solid rocket smokeless propellants, directly affecting the related performance of propellants and even rocket engines. Results showed that three primary initial decomposition mechanisms, namely, NNO2 bond dissociation, HONO elimination, and concerted ring fission, exist at both high and lower temperatures. Molecular vacancies affect how much each of the three pathways contributes to the initial breakdown of HMX, and these effects change with temperature. Molecular vacancies significantly enhance N-N bond cleavage and coordinated ring breaking at high temperatures (3200 K), while impeding the production of HONO bonds. The two main competing reaction pathways are N-N bond dissociation and HONO elimination, with the former being more prevalent during the first breakdown. Additionally, we calculated the first decomposition’s reaction rate constant and activation barriers for various vacancy concentrations. This RMD study showed that molecular vacancies accelerate the decomposition of condensed-phase HMX by increasing the reaction rate constant and reducing activation barriers.

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.The purpose of this research is to develop an exergy-based method to evaluate and compare different aircraft propulsion systems architectures to assist the design engineer at the early stages of product development. The method was successfully applied to a case study comprised of a baseline regional aircraft powered by gas turbines, which was compared to a hybrid-electric propulsion (HEP) version comprised of the gas turbines hybridized with batteries. The highest exergy efficiency of 33.5% was obtained for a configuration that presented a 5% degree of hybridization (DOH), defined as “power coming from batteries divided by total power”, and 800Wh/kg battery density. This corresponds to an increase of 0.7% when compared to the 32.8% efficiency of the baseline gas turbine. On the other hand, the aircraft total weight increased 2,160 kg, or 7.1%. Also, both the exergy consumption and exergy destruction increased with hybridization. For the flight mission, a remarkable increase of 2% to 7% was obtained for these parameters, as hybridization increased from 5% to 15%. On top of that, the HEP configuration saves 23 kg of jet fuel or 1% of fuel burn along the mission in comparison with the baseline. CO2 emissions reduction was around 70 kg per flight mission, as expected, since emissions increase proportionately with fuel consumption. Exergy-based emission costs and exergy destroyed in the kerosene refinery plant and in the electric power generation plant were also evaluated. Finally, some possible means to re-use the exergy lost in the aircraft propulsion system were presented and discussed.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.The use of sub-scales to study flight dynamics is an area that can provide excellent results. With the development of electronics, free flight tests to obtain flight dynamics data on sub-scale aircraft have become increasingly attractive. This paper presents the development of a sub-scale aircraft following the Froude number scaling technique used to achieve representativeness in flight dynamics.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.This article expands upon the analysis conducted in a flight campaign involving a flexible wing UAV with a 4m wingspan and an aspect ratio of 18.9, powered by electric propulsion. The UAV is equipped with a data acquisition system designed to explore the effects of flexibility. The initial phase of the campaign involved flight evaluations aimed at assessing the behavior of the system, particularly in terms of data acquisition. Data compatibility tests were examined using the Flight Path Reconstruction (FPR) technique and the Output Error Method (OEM). The outcomes of the FPR analysis indicate the consistency of the recorded data. The evaluation of biases, scale factors, and time delays using the FPR method successfully established correlations between the recorded data, with notable exceptions in the case of airspeed and angle of attack, which exhibited discrepancies in fitting with classic rigid body kinematics. In this work, the longitudinal FPR using OEM is augmented by incorporating the flexible aircraft dynamic model to provide a more accurate representation of the aircraft, accounting for flexibility effects. In the execution of the FPR, the state variables of the aircraft model, obtained by the integration of the kinematic expression and sensor-gathered data, were expanded by the addition of the structural dynamics. This modification has enabled the computation of α and β values at the vane positions, accounting for structural dynamics effects, and also evaluating accelerations at the wingtips. Synthetic data obtained from an aircraft simulation model were used to evaluate the FPR for the flexible aircraft, and the results have shown that this method can lead to good results when the aircraft model is available. The rigid and flexible FPR were applied to flight-recorded data, and the results obtained with the flexible FPR have not led to enhancements as seen in the simulated data, which indicates that further refinements must be made in the experimental procedures, and evaluations on the structural model and aircraft sensors must be conducted. In conclusion, the method can be used to evaluate additional information beyond the classic FPR developed solely relying on general rigid body kinematics.

© 2024, International Council of the Aeronautical Sciences. All rights reserved.With the development of electronics and programming in recent years, the possibility of aeronautical projects is being studied by academia and industry, with the aim of improving and adapting them to different projects for new applications and realities. One of these cases is the adaptation of projects such as the ground effect vehicles developed by the Soviet Union during the Cold War. This is an aircraft capable of flying close to the surface of the water and whose advantage is the energy saving of the propulsion of up to 40%. There are several companies developing projects of this type around the world, adapting them to the capacity and operating conditions of the different realities. In Brazil, the startup Aeroriver is developing a ground effect vehicle, the Volitan. This project aims to improve the transportation of people and cargo on the rivers of the Amazon. For the project to be successful, it is necessary to know up to what altitude this aircraft can fly to demonstrate energy savings, safety and maneuverability. A sub-scale prototype has been developed for initial testing and is currently being tested to determine the range and flight efficiency improvement of the Volitan in ground effect. Propulsion is provided by electric motors and power is supplied by a battery bank, allowing 15 minutes of flight autonomy. In this paper, the development of the electronics and instrumentation of a prototype is presented. In order to measure the efficiency of Volitan in flight, it will be equipped with load cells to measure the thrust force, RPM, the voltage and current consumed by the motors. Lidar to precisely measure the altitude in relation to the water, and a PixHawk controller used to record accelerations, speeds, position, attitude of the aircraft, etc. As results are presented the energy consumption of the batteries as a function of altitude, in flight condition in ground effect, as well as the thrust force generated by the motors, in addition to determining up to which altitude that the ground effect has a good performance and improves the efficiency of energy consumption of the Volitan.

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work proposes an assessment of the delta wing sweep variation of a Generic Future Fighter in the conceptual design phase. Combat aircraft have critical control and therefore the stability analysis of these configurations is compared. Little variation in stability was observed between the 5 different configurations. This indicates that other requirements may become more relevant when designing a fighter aircraft, such as stealth and performance. Thus, this work aims to evaluate the impact of wing sweep on the longitudinal stability of fighter aircraft, considering five different sweep angles: 45°, 47°, 50°, 55°, and 60°. To conduct this analysis, a numerical evaluation, using the Vortex Lattice Method (VLM), wind tunnel results and parameter identification data from past work will be used to obtain the aerodynamic data for each configuration. The aerodynamic data will then be used in a time-domain flight simulation model to analyze the longitudinal stability of the aircraft.