© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.This two-paper series proposes a unified theory that gives rise to a family of quasi-3D composite elements. The first paper presents the element formulation and its basic capabilities: the ability to capture transverse normal (σz) and shear (τyz, τxz) stresses, suitability for thermoelastic analyses and compliance to both displacements and transverse stress continuity requirements. These capabilities are inherent to the element since a global–local superposition approach is devised that, from inception, guarantees that equilibrium equations, continuity consistency and boundary conditions are fully met. A simple validation analysis was conducted in part I that initially pointed to a very promising direction with high numerical efficiency of the element. This second paper investigates the element numerical performance under different scenarios: use of three- and four-node parent elements, degree of global interpolation functions, adequacy of different local interpolation functions (F0, F1, G0, G1, H0, H1) and consideration of a more practical configuration of a reinforced panel consisting of multiple laminates. Through-the-thickness displacements, strains and stresses are obtained and shown to be of reasonable accuracy. Results are compared against a highly refined mesh of 3D brick elements implemented in a commercial software that provide a benchmark for the elements capabilities.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.In a series of two papers, a unified formulation for new plate composite elements is proposed that captures through-the-thickness effects, specifically normal and transverse shear stresses and strains. Thermal effects are also considered, including thermal effects through-the-thickness. This first paper is devoted to the fundamentals of the proposed unified formulation. The elements proposed are displacement based and the number of degrees of freedom is kept as small as possible, all of them possessing clear physical meaning. The elements are built using local functions defined at each layer and global functions defined along the thickness. The consistency of the kinematic assumptions is guaranteed through the imposition of displacement continuity along the thickness direction, transverse stress continuity and boundary conditions at the bottom and top surfaces of the elements. The formulations are developed for either isotropic or orthotropic materials. The formulations shall prove substantially more efficient than those based on solid elements traditionally used to capture normal transverse stresses. In the sequel, a second paper presents a variety of numerical results obtained using the proposed formulation and discusses its capabilities and potential.

© 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.Composite materials present challenging gaps to be studied due to their unique characteristics. The finite element method has been used to analyze composite materials subjected to the most distinctive situations. In the present work, the advantages of three element solutions studied previously are combined to develop a fourth element solution. First, decreasing the degree of the polynomials representing the axial displacement at the bottom and at the top surfaces circumvents shear locking in beams. Second, including the homogeneous solution ensures the continuity of the displacements between elements, but in this case the determination of the stiffness matrix requires a huge amount of computational time. However, it is shown that only modifications close to the original block diagonal matrix need to be considered, since far from the diagonal the contribution of the homogeneous solution is negligible. Additionally, a procedure is described to calculate a more accurate value for the stress σz.

© 2022 Elsevier Masson SASThe use of composite materials in several sectors has been gaining distinction in recent years. However, due to their high costs, as well as unique characteristics, they present challenging gaps to be studied. The finite element method has been used as a way to analyze composite materials subjected to the most distinctive situations. Three element solutions are compared, which can be applied to composite beams. The accuracy of the outcomes does not improve with higher degree polynomials, but the inclusion of the homogeneous solution to solve a system of differential equations results in a better outcome when considering the normal strains. Special attention is paid to the continuity of the displacements between adjacent elements. Finally, it is explained why the calculated axial normal stress looks much better than the transverse normal stress.

© 2021The determination of the fatigue behavior at a component level usually requires dedicated test rigs and an expressive amount of time. The hours spent on such machinery are expensive; therefore, solutions to reduce experimentation time are most welcomed. In this context, this investigation aims at developing a procedure for rapid determination of the fatigue strength of crankshafts by means of a thermographic methodology. The use of infrared cameras for fatigue strength analysis was first assessed in standard dog-bone specimens. Crankshafts were then tested in an in-house fatigue test rig using the conventional staircase method and the thermographic method. Sample batches with different manufacturing parameters were produced and tested to assess the robustness of the proposed alternative technique. Results of the dog-bone test campaign revealed a good correlation between fatigue strength estimates obtained with the conventional Wöhler curve and the thermographic methodology. Finally, the thermographic technique also delivered results in close agreement with the staircase method for all crankshaft batches. The proposed procedure was found to be a viable, rapid alternative to conventional fatigue test programs, with potential application for complex structural components such as crankshafts, among others.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.This work employs a micromechanical theory and kinematic relationships to describe the displacement field in individual unidirectional composite plies. The technique relies on an incremental approach where the misalignment angle of fibers is the main variable in the analysis. Upon convergence at a certain loading level, stresses and strains are evaluated in the fibers and matrix using micromechanics, and a specific failure criterion is applied. The Ramberg-Osgood relations are used to correct degraded mechanical properties of the resin in the nonlinear regime. The Hashin-Rotem failure criterion and experimental data obtained in the literature are used to validate the technique. It is observed that the numerical and experimental results obtained correlate well.

© 2022 American Chemical Society. All rights reserved.Shell-isolated nanoparticles (SHINs) with a 37 nm gold core and an 11 nm tin dioxide (SnO2) coating exhibited long-life Raman enhancement for 3 months and a wide pH stability of pH 2-13 in comparison with conventional SiO2-coated SHINs. Herein, Au-SnO2is demonstrated as a more durable SHIN for use in the technique Shell-Isolated Nanoparticles for Enhanced Raman Spectroscopy (SHINERS).

© 2022 American Chemical Society. All rights reserved.Theoretical insights have been gained into nickel adatom interaction with model platinum basal planes, and evolution of their fundamental properties with growing nickel surface coverage has been analyzed. Calculations have been performed using density functional theory with the Perdew-Burke-Ernzerhof exchange correlation functional and dipole corrections. The presence of a single Ni atom appreciably affects the Pt surface, lowering the work function and shifting the d-band center position away from the Fermi level of Pt atoms in contact with Ni. At increasing coverage, Ni bonding strength with Pt increases and plain structures are formed on all considered surfaces, although the initial tendencies, seen for the Pt fundamental properties upon Ni adsorption, do not change. Compared to reported experimental data, results suggest that lowering of the work function, φ, of Pt(111) upon Ni adsorption may facilitate charge transfer through the electric double layer, improving the rate of the hydrogen evolution reaction in alkaline media on Ni-modified Pt(111) surfaces. Hence, this rate-promoting effect would be expected to be lower for Pt(110) and (100) because of the lower impact of Ni adatoms on φ for these two surfaces. Results of the present study improve the current understanding of adatoms' electronic effects on the substrate and contribute to the scientific basis for the systematic design and development of Pt-based catalysts.

© 2021, Korean Society for Precision Engineering.Powder metallurgy represents an alternative to increase sustainability in the manufacturing of automotive gears, but its potential is hindered by a certain lack of knowledge on surface integrity properties that can impair the gear performance. This study explores the effects of the microstructural differences induced by this chain on the residual stress heterogeneity state of gears. X-ray diffraction methods of macro residual stress mapping and line profile analysis were applied for measurements of gear teeth after subsequent steps of the powder metallurgy and the conventional wrought steel chains. The powder metallurgy chain induced more pronounced heterogeneities than the conventional manufacturing, characterized by non-uniform residual stress distributions along the lead and the involute profiles of gear flanks. These non-uniformities observed after carburizing were traced back to the previous steps, surface densification, sintering and compaction. The residual stress distribution patterns of these steps were compatible with the plasticity dynamics of each manufacturing process. Such surface integrity heterogeneities result in a residual stress gradient along the gears functional surface, exposing particular regions to be more susceptible to fatigue effects.

© 2022 The Authors.The evolution of residual stress (RS) induced by laser powder bed fusion (L-PBF) along post-processing steps of automotive carburizing steels is a topic still underexplored by the scientific community. In this study, L-PBF specimens of 20MnCr5 steel produced with different build orientations were subjected to the same stress relief, milling and carburizing steps. RS and the diffractogram full width of half maximum (FWHM) depth profiles obtained through X-ray diffraction were compared along the manufacturing chains. It was shown that the previous manufacturing steps influence the final RS state, from L-PBF to carburizing.

© 2022 Elsevier Inc.In recent years, different dispersion-diffusion (eigen)analyses have been developed and used to assess various spectral element methods (SEMs) with regards to accuracy and stability, both of which are very important aspects for under-resolved computations of transitional and turbulent flows. Not surprisingly, eigenanalysis has been used recurrently to probe the inner-workings of SEM-based implicit LES approaches, where numerical dissipation acts alone in lieu of a subgrid model. In this study we present and discuss an intriguing linear mechanism that causes energy transfer across Fourier modes as seen in the energy spectrum of SEM computations. Despite its linear nature, this mechanism has not been considered in eigenanalyses so far, possibly due to its connection to the often overlooked multiple eigencurves feature of periodic eigenanalysis. As we unveil the mechanism in the simplified context of linear advection, we point out how its effects might take place in actual turbulence simulations. In particular, we highlight how taking it into account in eigenanalysis can improve dissipation estimates in wavenumber space, potentially allowing for a superior correlation between dissipation estimates and energy spectra measured in SEM-based eddy-resolving turbulence computations.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.An aircraft flying under icing conditions tends to accumulate ice on aerodynamic surfaces which deteriorates aircraft performance and may affect safety. Recent work obtained, via 3D-scanning, high-fidelity characterization of ice shapes generated in the NASA-CRM model swept wing in the NASA IRT icing wind tunnel. These shapes are highly three-dimensional and in order to better understand and isolate the effects of the three-dimensional parameters, various simplified shapes were built and tested in aerodynamic wind tunnels to compare the results with the high-fidelity representation. Even with this geometrical break-down, the aerodynamic phenomena that takes place in the highly swept wing of the NASA-CRM model are complex. The present work takes a step backwards in the complexity level, evaluating the threedimensional shapes effect on NACA 23012 airfoil, to provide basis for a better understanding of the NASA-CRM icing tests. The effects of horn ice shapes with different spanwise gaps sizes and orientations were evaluated by testing artificial ice shapes on the leading edge of a NACA 23012 airfoil under low-Reynolds-number conditions. The lift, drag, pitching moment and pressure distribution were measured for the clean airfoil and six ice shapes built. The aerodynamic performance and PIV measurements for each of these geometries are compared with its extruded 2D counterpart and clean airfoil configuration. The results regarding the size of the gaps in the ice shapes, showed that the increase in the gap widths directly improved airfoil performance. The PIV flow fields helped identify flow reattachment downstream the horn bubble for ice shapes with gaps. The surface oil visualization for the oriented ice shapes helped understand certain patterns and influence of the cross flow past the horn.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.It is well-known that ice accretion can adversely impact the aerodynamic performance of airfoils and wings. In this work, we conducted an experimental investigation on the impact of different ice shapes on the flow around airfoils. The NACA 23012 and the GLC-305 airfoils were tested at a low-reynolds wind tunnel, which included forces, moments and surface pressure were evaluated, and Particle Image Velocimetry (PIV) was used for flow field measurement. The studied ice type was a simulated single horn based on the glaze ice accreted on airfoil leading edge, with different heights and chord position. The parametric approach was applied in order to vary the ice geometric characteristics. Evaluation was performed with the ice shape extruded throughout the entire span of the airfoil, and the objective of this research was to provide a flowfield-physics perspective on the flow with different ice geometries and its effect on the overall aerodynamic performance of the airfoil under low Reynolds conditions.

© 2021 Elsevier B.V.One of the strengths of the discontinuous Galerkin (DG) method has been its balance between accuracy and robustness, which stems from DG's intrinsic (upwind) dissipation being biased towards high frequencies/wavenumbers. This is particularly useful in high Reynolds-number flow simulations where limitations on mesh resolution typically lead to potentially unstable under-resolved scales. In continuous Galerkin (CG) discretisations, similar properties are achievable through the addition of artificial diffusion such as spectral vanishing viscosity (SVV). However although SVV is recognised as very useful in CG-based high-fidelity turbulence simulations, this approach has been observed to be sub-optimal when compared to DG at intermediate polynomials orders (P≈3). In this paper we explore an alternative stabilisation approach through the introduction of a continuous interior penalty on the gradient discontinuity at elemental boundaries, which we refer to as a gradient jump penalisation (GJP). Analogous to DG methods, this introduces a penalisation at the elemental interfaces as opposed to the interior element stabilisation of SVV. Detailed eigenanalysis of the GJP approach shows its potential as equivalent (sometimes superior) to DG dissipation and hence superior to previous SVV approaches. Through eigenanalysis, a judicious choice of GJP's P-dependent scaling parameter is made and found to be consistent with previous a-priori error analysis. The favourable properties of the GJP stabilisation approach are also supported by turbulent flow simulations of the incompressible Navier–Stokes equation, as we achieve higher quality flow solutions at P=3 using GJP, whereas SVV performs marginally worse at P=5 with twice as many degrees of freedom in total.

© Spectral proper orthogonal decomposition (SPOD) is an increasingly popular modal analysis method in the field of fluid dynamics due to its specific properties: a linear system forced with white noise should have SPOD modes identical to response modes from resolvent analysis. The SPOD, coupled with the Welch method for spectral estimation, may require long time-resolved datasets. In this work, a linearised Ginzburg-Landau model is considered in order to study the method's convergence. Spectral proper orthogonal decomposition modes of the white-noise forced equation are computed and compared with corresponding response resolvent modes. The quantified error is shown to be related to the time length of Welch blocks (spectral window size) normalised by a convective time. Subsequently, an algorithm based on a temporal data shift is devised to further improve SPOD convergence and is applied to the Ginzburg-Landau system. Next, its efficacy is demonstrated in a numerical database of a boundary layer subject to bypass transition. The proposed approach achieves substantial improvement in mode convergence with smaller spectral window sizes with respect to the standard method. Furthermore, SPOD modes display growing wall-normal and spanwise velocity components along the streamwise direction, a feature which had not yet been observed and is also predicted by a global resolvent calculation. The shifting algorithm for the SPOD opens the possibility for using the method on datasets with time series of moderate duration, often produced by large simulations.

© 2022 American Physical Society.Reduced-order models were derived for plane Couette flow using Galerkin projection, with orthonormal basis functions taken as the leading controllability modes of the linearized Navier-Stokes system for a few low wave numbers. Resulting Galerkin systems comprise ordinary differential equations, with a number of degrees of freedom ranging from 144 to 600, which may be integrated to large times without any indication of numerical instability. The reduced-order models so obtained are also found to match statistics of direct numerical simulations at Reynolds number 500 and 1200 with reasonable accuracy, despite a truncation of orders of magnitude in the degrees of freedom of the system. The present models offer thus an interesting compromise between simplicity and accuracy in a canonical wall-bounded flow, with relatively few modes representing coherent structures in the flow and their dominant dynamics.

© 2022 authors. Published by the American Physical Society.Resolvent analysis has found applications in several areas of fluid mechanics, providing physical insight into both laminar and turbulent flows. In spite of such fact, the global (3D) resolvent is computationally expensive, which limits the size of the domain and the Reynolds number of the flows which can be considered. In this work, we derive a parabolic resolvent approach, which enables a significant increase in the computational efficiency of the calculation, for streaky structures in boundary layer flows. The computational speedup depends on the size of the problem and could be of more than one order of magnitude for the same accuracy as the global calculation. The method is derived based on an optimization method via the Lagrange multipliers over the linearized boundary layer equations and it is coupled to a Krylov-Arnoldi decomposition to the computation of suboptimals. The application of the method is exemplified for two problems: A Falkner-Skan boundary layer, where we obtain trends for both the optimals and suboptimals, and a turbulent boundary layer, where characteristics such as the double peak in the spectrum and the characteristic inner and outer length scales can be recovered when a variable eddy viscosity is considered. In both cases, a scaling is found for the dominant gain, given in terms of the fourth power of the Reynolds number, defined in terms of the relevant scale for the problem, the displacement thickness, and the modified Rotta-Clauser parameter for the laminar and turbulent boundary layers, respectively. For the laminar case, we further demonstrate that a forcing limited to the free-stream region is capable of generating streaky structures inside the boundary layer, a relevant feature for free-stream turbulence-induced transition.

© Self-similarity of wall-attached coherent structures in a turbulent channel at is explored by means of resolvent analysis. In this modelling framework, coherent structures are understood to arise as a response of the linearised mean-flow operator to generalised frequency-dependent Reynolds stresses, considered to act as an endogenous forcing. We assess the self-similarity of both the wall-attached flow structures and the associated forcing. The former are educed from direct numerical simulation data by finding the flow field correlated with the wall shear, whereas the latter is identified using a frequency space version of extended proper orthogonal decomposition (Borée, Exp. Fluids, vol. 35, issue 2, 2003, pp. 188-192). The forcing structures identified are compared to those obtained using the resolvent-based estimation introduced by Towne et al. (J. Fluid Mech., vol. 883, 2020, A17). The analysis reveals self-similarity of both wall-attached structures - in quantitative agreement with Townsend's hypothesis of self-similar attached eddies - and the underlying forcing, at least in certain components.

© The Author(s), 2022.The publisher apologises that upon publication of the article Martini, E., Jung, J., Cavalieri, A., Jordan, P. & Towne, A. (2022), two author affiliations were switched around. The full and correct author affiliations are: Eduardo Martini1,2, Junoh Jung3, André V.G. Cavalieri1, Peter Jordan2 and Aaron Towne3 1Instituto Tecnológico de Aeronáutica, 12228-900 São José dos Campos/SP, Brazil 2Département Fluides, Thermique et Combustion, Institut Pprime, CNRS, Université de Poitiers, ENSMA, 86000 Poitiers, France 3University of Michigan, Ann Arbor, MI 48109, USA The online version of this article has been updated.

© The Author(s), 2022. Published by Cambridge University PressThe application of control tools to complex flows frequently requires approximations, such as reduced-order models and/or simplified forcing assumptions, where these may be considered low rank or defined in terms of simplified statistics (e.g. white noise). In this work we propose a resolvent-based control methodology with causality imposed via a Wiener-Hopf formalism. Linear optimal causal estimation and control laws are obtained directly from full-rank, globally stable systems with arbitrary disturbance statistics, circumventing many drawbacks of alternative methods. We use efficient, matrix-free methods to construct the matrix Wiener-Hopf problem, and we implement a tailored method to solve the problem numerically. The approach naturally handles forcing terms with space-time colour; it allows inexpensive parametric investigation of sensor/actuator placement in scenarios where disturbances/targets are low rank; it is directly applicable to complex flows disturbed by high-rank forcing; it has lower cost in comparison to standard methods; it can be used in scenarios where an adjoint solver is not available; or it can be based exclusively on experimental data. The method is particularly well suited for the control of amplifier flows, for which optimal control approaches are typically robust. Validation of the approach is performed using the linearized Ginzburg-Landau equation. Flow over a backward-facing step perturbed by high-rank forcing is then considered. Sensor and actuator placement are investigated for this case, and we show that while the flow response downstream of the step is dominated by the Kelvin-Helmholtz mechanism, it has a complex, high-rank receptivity to incoming upstream perturbations, requiring multiple sensors for control.

© 2022 American Physical Society.This paper presents a study on wave cancellation in forced jets. Building on recent work on real-time control of forced turbulent jets by Maia et al. [Phys. Rev. Fluids 6, 123901 (2021)10.1103/PhysRevFluids.6.123901], we here assess the effect of jet upstream conditions and nonlinearity on wave-cancellation performance. The experiments are performed in jets with laminar and turbulent boundary layers inside the nozzle. An open-loop campaign is first conducted, in which the goal is to analyze the jet response to stochastic forcing with variable bandwidth. The upstream conditions of the jet are found to have a strong influence on the jet response. For narrow forcing bandwidths, both jets present a clear response regime. However, in the initially laminar jet, as bandwidth is increased, high growth rates and transition to turbulence in the initial region underpin the onset of nonlinear effects in jet response. In the initially turbulent jet, on the other hand, lower growth rates allow a linear response regime to be maintained for a broader range of forcing parameters. As the wave cancellation strategy is linear, reactive control is found to be more effective in the initially turbulent jet, consistent with the results of the open-loop analysis.

© 2021 The Author(s). Published by Cambridge University Press.The present work studies the nonlinear dynamics of a shear layer, driven by a body force and confined between parallel walls, a simplified setting to study transitional and turbulent shear layers. It was introduced by Nogueira & Cavalieri (J. Fluid Mech., vol. 907, 2021, A32), and is here studied using a reduced-order model based on a Galerkin projection of the Navier-Stokes system. By considering a confined shear layer with free-slip boundary conditions on the walls, periodic boundary conditions in streamwise and spanwise directions may be used, simplifying the system and enabling the use of methods of dynamical systems theory. A basis of eight modes is used in the Galerkin projection, representing the mean flow, Kelvin-Helmholtz vortices, rolls, streaks and oblique waves, structures observed in the cited work, and also present in shear layers and jets. A dynamical system is obtained, and its transition to chaos is studied. Increasing Reynolds number leads to pitchfork and Hopf bifurcations, and the latter leads to a limit cycle with amplitude modulation of vortices, as in the direct numerical simulations by Nogueira & Cavalieri. Further increase of leads to the appearance of a chaotic saddle, followed by the emergence of quasi-periodic and chaotic attractors. The chaotic attractors suffer a merging crisis for higher, leading to a chaotic dynamics with amplitude modulation and phase jumps of vortices. This is reminiscent of observations of coherent structures in turbulent jets, suggesting that the model represents a dynamics consistent with features of shear layers and jets.

© The Author(s), 2021. Published by Cambridge University Press.We present an analysis of the linear stability characteristics of shock-containing jets. The flow is linearised around a spatially periodic mean, which acts as a surrogate for a mean flow with a shock-cell structure, leading to a set of partial differential equations with periodic coefficients in space. Disturbances are written using the Floquet ansatz and Fourier modes in the streamwise direction, leading to an eigenvalue problem for the Floquet exponent. The characteristics of the solution are directly compared with the locally parallel case, and some of the features are similar. The inclusion of periodicity induces minor changes in the growth rate and phase velocity of the relevant modes for small shock amplitudes. On the other hand, the eigenfunctions are now subject to modulation related to the periodicity of the flow. Analysis of the spatiooral growth rates led to the identification of a saddle point between the Kelvin-Helmholtz mode and the guided jet mode, characterising an absolute instability mechanism. Frequencies and mode shapes related to the saddle points for two conditions (associated with axisymmetric and helical modes) are compared with screech frequencies and the most energetic coherent structures of screeching jets, resulting in a good agreement for both. The analysis shows that a periodic shock-cell structure has an impulse response that grows upstream, leading to oscillator behaviour. The results suggest that screech can occur in the absence of a nozzle, and that the upstream reflection condition is not essential for screech frequency selection. Connections to previous models are also discussed.

© 2022 12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022. All rights reserved.A resolvent-based methodology is employed to obtain non-causal spatio-temporal estimates of turbulent pipe flow from low-rank probe measurements of wall shear-stress fluctuations. DNS and LES pipe flow numerical simulations at friction Reynolds number of 550 are used as databases. We consider one of the DNS databases as the true spatio-temporal flow field, from which the low-rank measurements are extracted. Such database is also employed to verify the accuracy of the linear estimators. The estimator needs a model for the nonlinear (or forcing) terms of the Navier-Stokes equations system, which are obtained from a DNS database and from a series of computationally cheaper LES databases with grids coarser than the DNS. Comparisons between the reference DNS and the estimates indicate that sufficiently accurate results can be achieved with cheaper LES containing up to 10% of the number of grid points of the DNS, with estimates closely matching the reference DNS results up to the buffer-layer and reasonable agreement up to the beginning of the log layer.

© 2022 12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022. All rights reserved.Coherent structures are found in many different turbulent flows, and they are known to drive self-sustaining processes in minimal-unit turbulence. Identifying the triadic interactions between coherent structures can provide insights beyond what is possible in the framework of linearised models. There are infinite possible interactions that may generate a given structure, and thus a method to systematically study those, ranking them in terms of their contribution, is of interest. We here use the resolvent-based extended spectral proper orthogonal decomposition (RESPOD) approach (Karban, U. et al. 2022 Self-similar mechanisms in wall turbulence studied using resolvent analysis. Journal of Fluid Mechanics 969, A36) to identify the relevant triadic interactions for a minimal Couette flow at Reτ = 34, studying the interactions that give rise to wall-attached structures, obtained by measuring the wall-shear. Our analysis reveals that there are six triadic interactions that dominate the most-energetic wall-attached structure.

© 2022 12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022. All rights reserved.We propose a formulation to study the effect of streaks in the spatial development of wavepackets. To this end, a modified version of the parabolised stability equations (PSE) linearized around a streak-containing mean flow is used, which considers a series of azimuthal wavenumbers in the solution. In the present case, streaks are obtained from experiments using spectral proper orthogonal decomposition applied to particle image velocimetry data, and extrapolated in the radial direction using a Gaussian fit. Streaks and rolls predicted by resolvent analysis are also used in the analysis to evaluate the effect of streamwise vortices in the development of the noise-generating structures. Results show that streaks non-trivially modify the spatial support of the Kelvin-Helmholtz wavepackets and their phase velocity, which may lead to changes in the sound generation efficiency of the jet. New structures across the shear layer induced by the presence of streaks are also observed further downstream for high streak amplitudes.

© 2022, AIAA International. All rights reserved.The present work is dedicated to the modeling of the low-frequency part of the jet installation noise (JIN) in flight conditions. It is known that the properties of JIN can be predicted based on the characteristics of the near field of an isolated jet. Unlike the static case, in the presence of a coflow, it is difficult to directly measure the structure of the pressure perturbations in the jet near field. To overcome this problem, we propose a technique based on hot-wire measurements on the jet axis, suitable both for static and flight conditions. The well-known agreement between a parabolized stability equations (PSEs) model and experimentally measured velocity fluctuations on the jet axis allows using the PSE approach for the reconstruction of the axisymmetric pressure fluctuations in the vicinity of the wing trailing-edge location. The first helical mode, which is also important for the jet installation noise prediction, is approximately reconstructed based on the fact that its properties are close to those of the axisymmetric mode. These pressure characteristics are then used as input in an analytical jet installation noise model. To confirm this approach, acoustic measurements of JIN in static and flight conditions are conducted for a laboratory subsonic jet installed near a flat plate simulating a wing. It is shown that the analytical model informed by the PSE-reconstructed pressure field is capable of capturing the main features of the low-frequency jet–plate interaction noise both in static conditions and in the presence of coflow.

© 2022, AIAA International. All rights reserved.The effect of addition of viscoelastic plies on the acoustic scattering quadrupoles near the trailing edge of laminated plates is evaluated. A numerical method is applied to compute the acoustic field scattered by finite flexible plates. For a two-dimensional problem whereby a cantilevered plate scatters sound from a point quadrupole near the free edge, results show that adding viscoelastic layers to a composite plate can modify the far-field sound. Parametric investigations show that this treatment reduces scattered noise near resonance frequencies. Discussions on the positioning and thickness of the viscoelastic layers and operating temperature are provided. The use of outer viscoelastic layers in composite plates is predicted to significantly reduce acoustic scattering near resonances due to structural damping.

© 2022 by the authors. and Astronautics, Inc.,.Control law design for flexible aircraft with coupled flight and structural dynamics is currently a challenge. If not correctly addressed during control law design, the aeroservoelastic coupling can negatively affect the lateral-directional stability of the aircraft. In this context, this paper describes a methodology for the design of a stability augmentation system for the Instituto Tecnológico de Aeronáutica X-HALE flexible aircraft and proposes a performance index for numerical optimization of the closed-loop feedback gains. Comparisons between open-loop and closed-loop numerical simulation results show how the proposed control system attenuates the Dutch-roll response. An aeroservoelastic analysis is made in which it its demonstrated that the control system has small but beneficial effects on aeroelastic stability. Finally, experimental data obtained via flight tests with the real aircraft demonstrate the effectiveness of the control system in practice.

© 2022 Elsevier LtdThe corrosion behaviour of laser and plasma nitrided β-Ti12Mo6Zr2Fe biomaterial was evaluated. Polarisation curves and electrochemical impedance spectroscopy were performed in simulated body fluid (SBF) at 37 °C. Both treatments formed titanium-nitride at the alloy's surface, and significantly improved the corrosion performance of the alloy. At anodic potentials of the order of 1.0 V, the titanium-nitride layer seems to oxidise, independent of the nitriding process. Nanometric fissures formed on the plasma titanium-nitride layer seems to govern the impedance response at low frequencies, exposing the substrate to the electrolyte. Laser titanium-nitride layer is thicker and lead to a better corrosion performance.

© 2022 Elsevier B.V.Patients with skin diseases may have their quality of life affected. Many of them have chronic skin lesions or some form of complication during the healing process. Ozone therapy is a low-cost method with efficient results, including the easy application of ozonized oil to the skin. However, studies report divergent times for the ozonation process of vegetable oil. This work aims to characterize, using the Fourier transform infrared (FT-IR) spectroscopy technique, sunflower oil ozonized at different exposure times. Nine samples of oil were treated up to 90 min with ozone (maximum applied ozone dosage of 117.0 g L−1) and, together with the control sample, were analyzed by FT-IR and the spectra deconvoluted in relation to the main bands observed by the second derivative. Two spectral regions were investigated: 1800 – 800 cm−1 and 3050 – 2800 cm−1. The results indicated a statistically significant difference between the spectra, especially after 20 min of the ozonation process. A decrease in oil temperature was observed 30 min after the beginning of the ozonation process, with a decrease in the intensity of the –CH stretching band of the fragment –C[dbnd]C–H above 3000 cm−1, an increase of the intensity of the C–H stretching bands of the CH3 groups, decrease of intensity of the stretching bands of –C[dbnd]C– chemical bond, and constant intensity of the –C[dbnd]O stretching band.

© 2022 by the authors.The growing need for increasingly miniaturized devices has placed high importance and demands on nanofabrication technologies with high-quality, low temperatures, and low-cost techniques. In the past few years, the development and recent advances in atomic layer deposition (ALD) processes boosted interest in their use in advanced electronic and nano/microelectromechanical systems (NEMS/MEMS) device manufacturing. In this context, non-thermal plasma (NTP) technology has been highlighted because it allowed the ALD technique to expand its process window and the fabrication of several nanomaterials at reduced temperatures, allowing thermosensitive substrates to be covered with good formability and uniformity. In this review article, we comprehensively describe how the NTP changed the ALD universe and expanded it in device fabrication for different applications. We also present an overview of the efforts and developed strategies to gather the NTP and ALD technologies with the consecutive formation of plasma-assisted ALD (PA-ALD) technique, which has been successfully applied in nanofabrication and surface modification. The advantages and limitations currently faced by this technique are presented and discussed. We conclude this review by showing the atomic layer etching (ALE) technique, another development of NTP and ALD junction that has gained more and more attention by allowing significant advancements in plasma-assisted nanofabrication.

© 2022 by the authors.This work reports on the (zero-dimensional) global model study of argon plasma chemistry for a cylindrical thruster based on inductively coupled plasma (ICP) whose output has a system of two grids polarized with each other with direct current potential. The global model developed is based on particle and energy balance equations, where the latter considers both charged and neutral species. Thus, the model allows the determination of the neutral gas temperature. Finally, this study also investigated the role of excited species in plasma chemistry especially in the ions production and its implications for propulsion parameters, such as thrust. For this, the study was carried out in two different scenarios: (1) one taking into account the metastable species Arr and Arp (multi-step ionization), and (2) the other without these species (single-step ionization). Results indicates a distinct behavior of electron temperature with radiofrequency (RF) power for the investigated cases. On the other hand, the gas temperature is almost the same for investigated power range of up to 900 W. Concern propulsion analysis, a thrust of 40 mN at 450 W was verified for case (1), which represents a remarkable thrust value for electric thrusters.

© 2022 Elsevier LtdThe management of radioactive waste is a worldwide activity based on the guidelines of the International Atomic Energy Agency (IAEA), and all stages of management require scientifically proven methods for possible deployment. The management of radioactive waste is a huge challenge due to the high risk in the collection, gathering, transport, handling, and storage. In this study, a thermal plasma treatment process was evaluated for its efficiency to process solid radioactive waste. Experiments were carried out with the application of stable isotopes of Lead, Iodine, Cobalt, and Cesium. After the thermal plasma treatments, the slag and the residual gas were analyzed to verify the influence of process time and discharge power on the efficiency of the process. The treatment for 25 min and 10 kW was sufficient to reduce the mass by 50% of the slag. When the applied power was increased to 15 kW, an expressive reduction in the treatment time (10 min) was able to promote the same mass reduction. The results indicated that the treatment of radioactive waste by thermal plasma is a promising method to manage and reduce the mass and volume for the final disposal.

© 2023 Elsevier Inc. All rights reserved.Solar cells and photovoltaic devices are based overall on metal oxides and heterostructures. This is a technology in advance, with remarkable interest due to its low impact on the environment in comparison to the most used forms of energy conversion. Additionally, the oxides are most abundant, easy, and less expensive to obtain compared to other materials for such applications. Although the metal oxide–based photovoltaic devices show, usually, low conversion efficiency, some studies have shown capable of obtaining PCE higher than 10% or 20% using enhanced heterostructures. This chapter presented a review of the state of the art of metal oxide heterostructures applied mainly in photovoltaic devices and solar cells. A special focus is given to studies related to some of the most applied materials, such as ZnO, ZnO:Al, (AZO), and TiO2, and to heterostructures based on metallic oxides of copper, zinc, magnesium, vanadium, etc.

© 2022 The Author(s).Background. New surface treatments have been proposed to expand the clinical indications of zirconia prostheses. This study aimed to evaluate the effect of silica and fluorine nanofilms on zirconia ceramic on the resin cement bond strength. Methods. Zirconia blocks and discs underwent different surface treatments: untreated zirconia (CON), sandblasted, silica-coated alumina particles (30 µm) (SC), silica nanofilm (SN), and fluorine nanofilm (FN). Nanofilm deposition was performed through plasma enhanced chemical vapor deposition (PECVD). Zirconia surfaces were characterized on disks by morphology (atomic force microscopy, AFM), chemical analysis (x-ray photoelectron spectroscopy, XPS), and contact angle analysis. A silane coupling agent was applied on each treated surface, and a cylinder of resin cement was built up. Half of the specimens in each group were submitted to 6000 thermal cycles (TC). Bond strength was analyzed using the shear test, and the fractographic analysis was performed with stereomicroscopy and SEM/EDS. Statistical analysis was performed through one-way ANOVA and Tukey test in the non-aged and aged specimens. Results. Nanofilms modified the zirconia surface, which became more hydrophilic and chemically reactive. Chemical bonding between Si-O was found in SN, and FN promoted a fluorination process on the ceramic surface, converting zirconia into zirconium oxyfluoride. Specimens of the SN (TC) group failed on pre-testing. FN (TC) bond strength (3.8 MPa) was lower than SC (TC) and CON (TC) after shearing. Adhesive failure predominated in the experimental groups. Silica nanofilm failure occurred after aging. Conclusion. Silica and fluorine nanofilms deposited by PECVD did not promote effective bonding between zirconia and resin cement.

© 2022 Universidade Federal de Sao Carlos. All rights reserved.This work reports the properties of GaN films grown onto c-Si (100) at relatively low substrate temperature (400°C) by reactive magnetron sputtering. The study depicts the effect of working pressure and RF power on the GaN film structural, vibrational and optical properties characterized by X-ray diffraction, atomic force and scanning electron microscopies, Raman spectroscopy and spectroscopic ellipsometry. Unusual low pressure deposition condition (0.40 Pa) was achieved by using a separated argon inlet directed to the Ga target surface, resulting in improved crystalline quality of the films. In this condition, the preferential crystalline orientation, the surface morphology and the optical gap of the GaN films show a strong dependence on the RF power applied to the Ga target, where low RF power (30-60 W) was responsible for increasing the c-axis orientation and the optical gap, while higher RF power (75-90 W) decreased the overall crystal quality and increased the surface roughness.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.The costs involved in the design, manufacture, certification and maintenance of a helicopter have grown over the past few years. In the certification phase of embedded systems, their safety levels and their performance requirements are verified. The helicopter engine is a system that must be reliable and capable of providing the necessary power to produce lift and controllability for the aircraft. In this work was developed a computer model to evaluate the helicopter engine’s performance under any flight conditions and the pilot’s inputs. The developed software was incorporated as a module in a flight test simulator at the Flight Tests and Research Institute (IPEV) which belongs to the Brazilian Air Force. This simulation tool allows foreseeing and investigating possible situations that may occur during actual flight tests, improving safety and reducing costs. Using MATLAB® Simulink, it was possible to run at the same time: an iterative and a non-iterative methodology, a control system to set the fuel flow schedule, based on several inputs generated from the thermodynamic model. Based on classic thermodynamics laws and differential equations, the particularities due to the helicopter application were adjusted: the influence of the pilot’s commands; performance requirements; running line control; and the fuel flow control system. The simulation results were compared with commercial gas turbine performance simulation software and with the data provided by the IPEV in five real flight tests. These data were also used for obtaining engine output power requirements according to collective stick position.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.The tip clearance is the gap between the rotor blade row and its casing. In this region, a leakage flow on the rotor blade tip is induced by pressure differences from rotor blade pressure side to suction side, resulting in a loss in the turbomachine efficiency and drop in performance. High pressure turbines (HPT) operate in the limit of the energy transfer process with low-aspect ratio blades and high-pressure loading. The tip clearance loss is significant when compared with other loss sources. To minimize the performance drop, different desensitization techniques were tested for turbulent flow in steady state. First, the HPT developed by NASA in the Energy Efficient Engine (E3) program was studied with its original configuration of rotor tip, also called flat-tip. Then, the winglet was implemented on rotor tip geometry, for both suction and pressure sides. Numerical simulations using the computational fluid dynamics were performed, and the results are compared with experimental data for both cases. The results show that in general, for the same HPT pressure ratio, the use of winglet on the rotor tip pressure side achieved the best results showing an increase in efficiency of 1.025 % for 3.7 of pressure ratio. Even the winglet on the rotor tip suction side presented an efficiency increase of 0.625 % for 3.7 of pressure ratio compared with flat-tip rotor configuration. Overall, both winglet configurations obtained results better than the common rotor blade flat-tip geometry, for the same pressure ratio operational condition.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.For a long time, thermal power plants play important roles in world electricity and are expected to continue, at least, in the next decades. However, the finitude of fossil fuel sources leads to the crucial need for improving the existing power generation systems. In this study, an in-house computational code was developed and validated to evaluate the energy, exergy and economic performance for thermal power plants applications. Based on operating data of an actual lignite coal-fired steam power plant, two cycles were designed and compared. In the cycle in which more components were added, the fuel consumption was 9.44% lower to produce the same amount of power, making more effective use of the fuel resource. This substantial reduction in fuel consumption reflected lower electricity average costs for this plant. Comparing to the electricity price of a country using the same type of fuel, it was found that it could be lower by 1.62 percentage points for household consumers. Although the higher costs with capital investment and operational and maintenance (O&M) due to the addition of these components, the attractive economic performance of the cycle reduces the annual fuel costs and offsets the increase in capital and O&M costs.

© 2022 Elsevier Masson SASAxial turbines are machines widely used in different engineering applications. Due to their constructive characteristics, they must have a space between the rotor blades and the turbine casing, called tip clearance. Unfortunately, this gap allows a part of the fluid to leak from the pressure side to the suction side of the rotor blades. This leakage is undesirable and represents an energy loss. A way to avoid part of this loss is through the use of desensitization techniques. Although the use of these techniques is widely known, no studies in the open literature have evaluated these techniques in hydraulic turbines. This work presents a numerical analysis of squealer desensitization techniques applied in a hydraulic axial turbine. The turbomachine under study is the first stage of the hydraulic axial turbine used in the Low Pressure Oxidizer Turbopump (LPOTP) of the Space Shuttle Main Engine (SSME). Numerical simulations were performed using CFX v.19.2 software, and computational meshes were generated in ICEM v.19.2 software. Initially, the computational model was validated, using the experimental results published by the National Aeronautics and Space Administration (NASA). A parametric analysis was performed considering the variation in squealer cavity depth and rim thickness. The study found that the squealer cavity depth has a greater influence on the stage performance than its rim thickness. The tendency is that the greater the cavity depth, the greater the stage efficiency. One of the squealer geometries analyzed allowed an average increased efficiency of 1.43%, over the entire turbine operational range. The results obtained also show that the application of the proposed geometries would enable the reduction in cavitation close to the trailing edge of the rotor blades. This result is extremely valuable, as it can impact the life cycle of the turbine.

© 2021 Elsevier Inc.The present work describes the implementation of an implicit time-integration numerical scheme to solve viscous flows in an in-house CFD solver. The scheme is developed to calculate engineering problems involving compressible flows. This work extends the defect-correction technique for the 3D flow calculations, and all mathematical formulations are described. The CFD solver is based on the finite-volume method (FVM) to calculate the three-dimensional flow and can be applied to solve unstructured meshes. The current implementation uses the Flux-Difference Splitting method (FDS) developed by Roe combined with the MUSCL method and the Venkatakrishnan flux limiters to provide better accuracy of the numerical solutions. The implicit time-integration scheme was linearized applying the backward Euler method on the left-hand side (LHS) and a Newton-type linearization on the right-hand side (RHS) of the governing equations. The Jacobian matrix was computed analytically for the inviscid fluxes using the Roe fluxes, and for the viscous fluxes differentiating the conservative vector. Earlier work by Cavalca et al. (2018) showed the robustness and accuracy of this implicit solver to predict inviscid flows over the airfoil and into the supersonic nozzle. Finally, the Gauss-Seidel (GS) iterative method was applied to solve the resultant sparse and large system of equations. These numerical schemes and methods were applied to solve the laminar flow over a flat plate. Afterwards, the numerical solution was validated and verified with the exact Blasius solution. From the results, the numerical simulations exhibited superior robustness of the implicit-defect correction scheme when compared with the explicit scheme for compressible flows. All numerical particularities and their implementations are detailed in this paper.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.Variable cycle engines promise to enable adaptive cycles that give close to optimal performance over a wide range of conflicting mission requirements, such as low altitude high speed flight and supercruise still providing excellent range. Modelling such engines pose challenges for general purpose software since variable geometry gas paths modify the underlying set of equations being solved. It is possible to use multiple engine models transferring design data between the models. This, however, creates a high risk for inconsistency and modelling error. It is more attractive if the solutions obtained could be determined using the same model. In this work an in-house software was developed to model an Adaptive Cycle Engine (ACE). This development was used to show how variable cycle mode switches can be integrated into general purpose performance tools. The variable cycle engine uses a FLADE, which is a "fan on blade" component, to extend its range and to provide improved subsonic performance. The individual impact of the components, its effect on propulsion performance parameters and in the engine installation were analyzed as the main results. The contribution from this paper is thus two-fold, firstly the paper goes ahead and proposes new methods for the simulation of mode switching in generic performance tools by introducing dynamic equation systems. Secondly, the paper then studies the FLADE component and its potential performance benefits if added to a conventional turbofan architecture.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.An Axial Turbine Blade Tip has a great influence on its flow behavior and performance. Due to the clearance between the turbine casing and the rotor blades tips, part of the flow leaks from the pressure side to the suction side. This leakage reduces the turbomachine efficiency, and therefore must be minimized. Over the years, the use of desensitization techniques has proven to be an excellent strategy for reducing this unwanted flow. These techniques, however, has only been studied in machines that operate with compressible fluids. The objective of this work is to verify the effects of two Winglet geometries in the first stage of the Liquid Oxygen (LOX) Turbine used as booster in the Space Shuttle Main Engine (SSME). The two Winglet geometries evaluated have identical thickness and width, being differentiated by their trailing edge region configuration. In this region, the first geometry (W1) connects to the trailing edge with an angle close to 90°, while the second geometry (W2) presents a smooth connection. The results obtained show that it is possible to improve the stage efficiency depending on the geometry adopted, as well as to analyze the cavitation phenomenon. The mesh generation and simulations were done using a commercial software and the 3D flow calculations were based on the Reynolds Averaged Navier-Stokes (RANS) equations.

Copyright © 2022 by ASME.The gas turbine industry requires extensive knowledge in several areas of engineering, and since both industry and academy continuously develop new approaches, technologies, and models, usually, there is not enough time to cover all the relevant subjects in one or two-semester courses for undergraduate or graduate students. In previous work, the authors have presented an interactive platform for the preliminary design of single-stage axial turbines with uncooled blades, for use at the undergraduate courses offered by the Turbomachine Department at Aeronautics Institute of Technology to accelerate the learning process. The present work aims to present an expansion of this interactive learning platform, with the inclusion of a module for the thermodynamic cycle study, a module for off-design calculations, and the generation of a PDF file containing the step-by-step solution memorial with all the equations and values used in the design. The work also presents a structure for the conduction of a graduate course in turbomachines focused on the design of axial turbines. It comprehends theory and exercise classes, oriented study with the interactive learning platform, and a project in which the students have to implement some of the modules and run test cases. The authors observed more interest of the students and higher quality questions in the classes while using the interactive platform or programming, developing a better understanding of the design process until the end of the course. Also, while, in previous semesters, the preliminary design occupied almost half of the 48-hour course, it took only 12-hour to cover the same subject, granting time to more advanced topics, such as blade cooling, off-design performance and computational fluid dynamics simulations.

Copyright © 2022 by ASME.Passive wall treatments with circumferential grooves in axial compressors proved to be effective in increasing the compressor stall margin in previous researches by creating a resistance to the flow that leaks in the tip clearance region of the compressor, from the rotor blade pressure side to the suction side. 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 rotor row used in a four-stage axial flow compressor. 3D CFD flow simulations were performed in order to evaluate all the specified configurations aiming to find improvements on compressor stall margin. Investigations on the compressor flow characteristics were realized and the stall margin variations were determined. The numerical simulations were performed based on the Reynolds-Averaged Navier Stokes equations and the turbulence model was the k-ω SST. After the simulations, several rotational speeds of the compressor map characteristics, including the design-point rotational speed, were obtained for the case without casing treatment (smooth wall case) and for the case with circumferential grooves. In the results, passive wall treatment with circumferential grooves demonstrated an improvement in the compressor stall margin, especially for N=0.60 and N=0.90 rotational speeds.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA., All rights reserved.This work investigates the use of solid and permeable surfaces in the Ffowcs WilliamsHawkings (FW-H) analogy for predicting high-speed propeller noise. The CFD/CAA methodology encompasses unsteady Reynolds-Averaged Navier-Stokes simulations to compute the flowfield on the acoustic surface applied in the FWH analogy to obtain the noise signatures in the far-field. Furthermore, this manuscript also investigates the effects of the downstream end-cap position, on the propeller noise prediction, by using two permeable surfaces with different lengths to assess the propeller noise levels in each case. The former is a short SFW-H surface placed near the rotor, and the latter, namely the LFW-H, is a surface larger in length where the end-cap grid is placed farther downstream from the rotor. The results showed the capability of the permeable surface technique for predicting the noise with higher accuracy than the solid formulation, especially at the first blade passing frequency. Also, the larger LFW-H surface performed better than the SFW-H surface. A reason that could justify this is that the LFW-H end-cap surface is placed at a suitable distance downstream from the propeller. Therefore, the LFW-H surface can include more of the contributions of the non-linear effects or quadrupole sources enclosed within the permeable source surface region.

© 2022, American Institute of Aeronautics and Astronautics Inc.. All rights reserved.Waste heat recovery is a key pathway to achieving reduced emissions and improved system efficiency. Waste heat can potentially be converted to electric power by several methods. One of the most effective methods is based on using a supercritical CO2 waste heat recovery power system. The sCO2 power system has advantages because of component compactness, which is an important consideration for aircraft integration. The present work focuses on implementing the supercritical CO2 power system into both current and next-generation aircraft engines that may use different fuels, such as hydrogen, ammonia, or sustainable aviation fuel (SAF). The first part of the work is focused on detailed optimization of the sCO2 waste heat system for a real aircraft engine with two sCO2 cycle configurations. The second part of the work is focused on detailed design of the heat exchangers, including weight and pressure drop calculation. The simulation was done using an in-house computer program for gas turbine performance and for the sCO2 cycle. The results show the potential utilization of waste heat in different operational regimes: idling on the ground, cruise, landing, and takeoff. One engine (nominal thrust of 9kN) with two different waste recovery units are investigated. The results demonstrated that the waste heat unit could generate an additional 100-200 kW for the 9-kN-engine (under cruise operation), which may reduce fuel consumption, even if the sCO2 system weight is around 800 lbm / 364 kg.

© 2021 Elsevier LtdThe requirements of Liquid Propellant Rocket Engine (LPRE) are high for thrust, specific impulse, and flow rate; thus, its components also have strict requirements. For the turbopumps (TPs), this means high flow rate, high rotational speed, and high pressure ratio, which makes their operations susceptible to the cavitation phenomenon, as observed in two previous works. In the first, cavitation regions were observed in the first stage of the Space Shuttle Main Engine (SSME) Liquid Oxygen (LOX) booster turbine, for 3.0, 5.5, and 8.0% tip clearances (relative to rotor blade height), using monophase flow (Lindquist Whitacker et al., 2017). In the second, the simulations were performed with multiphase flow, producing results more physically coherent for the 3.0% gap configuration (Whitacker et al., 2018). The characteristics of both types of simulations in space propulsion applications still require better understanding. Therefore, to compare monophase and multiphase results at various operating points and turbine configurations, steady-state turbulent 3-D Computational Fluid Dynamics (CFD) simulations were performed, based on Reynolds-Averaged Navier-Stokes (RANS) formulation. The same three tip configurations for the turbine first stage were simulated, and the calculations were validated using experimental results from the National Aeronautics and Space Administration (NASA) (Boynton and Rohlik, 1976). This made it possible to verify the effect of the tip clearance on the machine performance and internal flowfield. When the gap increased, the pressure loading decreased in a large region of the blade tip, the interaction was greater between the Tip Clearance Vortex (TCV) and a vortex generated around the shroud cavitation region (Cavitation Vortex - CV), and this interaction moved towards the middle of the blade-to-blade passage. Thus, the losses increased and the efficiency decreased. Various comparative aspects between the simulations using both mono and multiphase numerical schemes are also discussed.

© 2022 ISAThe present paper is concerned with the robust and smooth attitude-position tracking control of fully actuated multirotor aerial vehicles equipped with fixed rotors and subject to matched model uncertainties and disturbances. The vehicle coupled dynamic equations representing the translational and rotational motions are thoroughly derived using the multibody approach, considering the external torque and force disturbances as well as the uncertainties in the inertia parameters of the airframe and the rotors. From this model, it is shown that the overall disturbances and uncertainties can be lumped into an additive-matched plant-model discrepancy. Then, based on a geometrically consistent description of the control error in SE(3), a novel joint geometric attitude-position control law is designed using a multi-input smooth second-order sliding mode strategy. The latter uses a high-order sliding mode disturbance observer to guarantee the overall system robustness. The second-order sliding mode is proved to exist using vector-field homogeneity, and the tracking error is shown to exponentially converge to the origin. The method is extensively evaluated via numerical simulations using a fully actuated hexacopter with tilted rotors, showing advantages with respect to state-of-the-art alternatives.

© 2021 ISAThe present paper is concerned with the wayset-based guidance of underactuated multirotor aerial vehicles (MAVs). A hierarchical guidance and control structure is first established, in which the guidance is realized as a supervisory loop. The lower-level stabilizing attitude and position control laws are assumed to be available. On the other hand, the outer-loop guidance is designed based on a fixed-horizon tube-based robust model predictive control (MPC), which conducts the MAV to visit a given sequence of waysets, without violating their state and control bounds, and allowing the vehicle to rest in each wayset for a specified period. The MPC is designed using a reduced-order closed-loop dynamic model describing the vehicle's translation, which is derived considering the stabilizing position and attitude control laws and the assumption of a time-scale separation between the closed-loop translational and rotational dynamics. This model is put into a discrete-time linear state–space representation subject to additive bounded random disturbance and measurement noise. The properties of the proposed method, which includes the MPC recursive feasibility and robust stability as well as the overall guidance feasibility, are analytically studied. The method is also numerically evaluated using a realistic quadrotor dynamic model, showing its effectiveness and confirming its properties.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.The study of inverted pendulum configurations has attracted the attention of researchers during many decades. One of the main reasons is that inverted-pendulum models have the feature of approximating the dynamics of many real-world mechanisms. Therefore, this paper presents the detailed dynamic modeling and control of a novel spherical pendulum with a variable speed control moment gyroscope. The dynamic model is obtained from the generic 3D pendulum, and the necessary assumptions to model the spherical pendulum are conducted in order to avoid singularities. Furthermore, a proportional-derivative nonlinear controller based on Lyapunov theory is designed to use favorably the features of the variable speed control moment gyroscope to control the spherical pendulum combining the gyroscopic torque and the torque provided by the reaction wheel. The proposed dynamic model and nonlinear controller are evaluated through numerical simulations for two different scenarios, driving the pendulum to a sequence of attitude commands including the upright position and tracking a desired trajectory. The results have shown that the proposed model is nonsingular and that the control law has provided adequate rates controlling the pendulum in both scenarios.

© 2022, The Author(s), under exclusive licence to Springer Nature B.V.Researchers have been interested in the dynamics and control of pendulums for many decades since the mathematical models of these systems are able to represent the dynamics of real-world applications such as satellite launchers and balancing robots. This paper derives a novel multi-input global predefined-time sliding mode control strategy for the attitude control of a 3D pendulum. A different sliding variable is proposed assuring the convergence of the system to the equilibrium within a predefined time chosen by the designer in advance. Numerical simulations are carried out to evaluate the proposed controller in two different scenarios: taking the pendulum from the downward position to the upright position and tracking a sinusoidal reference. The results have shown that by using the proposed controller the system’s dynamics reaches the desired references within the predefined time, while being less conservative than other existing controllers.

© 2021 ISAThe present work is concerned with the wayset-based guidance of a very general class of fully-actuated multirotor aerial vehicles which can be equipped with fixed or vectorable rotors. The problem is tackled by means of a hierarchical guidance and control framework containing two nested loops. For the outer loop, a guidance strategy based on the nonlinear model predictive control paradigm is proposed. It steers the vehicle through a sequence of position-attitude waysets, while guaranteeing the satisfaction of the control allocation constraints. For the inner loop, a single multi-variable inverse-dynamic force–torque control law is designed to stabilize the translational and rotational dynamics, and an optimal control allocator is formulated, by means of a convex program, to distribute the required control efforts among the available actuators. The asymptotic stability of the inner and outer loop, the recursive feasibility of the guidance algorithm, as well as the feasibility of the control allocator are proved to hold. The proposed method is numerically illustrated with a quadrotor containing two-degrees-of-freedom vectorable rotors and shows to be effective to guide the vehicle while respecting all the rotor constraints.

© 2022 Elsevier Masson SASThe present work deals with the optimal control allocation of fully actuated multirotor aerial vehicles (MAVs) equipped with fixed (non-vectoring and constant-pitch) rotors. To tackle the problem, a cascaded control architecture is considered in which the control allocation is separated from the control law itself. The latter provides the resulting control efforts (three-dimensional force and torque) from the desired state trajectory, while the former is entrusted to distribute the resulting control efforts among the available actuators. The control allocation is formulated as a convex optimization problem, which, on the one hand, unifies the previous methods and, on the other hand, extends the literature by rigorously considering the rotors' dynamics and bounds, thus resulting in a novel constrained optimal control allocation algorithm suitable for quite general fixed-rotor fully actuated MAVs. Moreover, a control-allocation feasibility analysis based on the control allocator admissible set is presented. It provides a necessary and sufficient condition for the existence of a solution to the control allocation problem. We argue that this condition can be explicitly used in the design of the control law, thus improving its synergy with the control allocator. The proposed control allocation method is mathematically analyzed and widely illustrated by the computer simulation of two non-planar omnidirectional MAVs.

© 2022 ICAS. All Rights Reserved.The ability of multiple manned and unmanned aircraft systems to cooperatively engage and disable an aerial threat plays a decisive role in modern warfare scenarios. In this paper, we apply key methods to enable the so-called cooperative threat engagement capability among multiple networked agents, e.g., a swarm of drones, with combat and communication capabilities. In particular, this research combines AI-based decision-making and control techniques for a swarm of loyal wingman drones to coordinate efficient defense actions in cooperative and autonomous manner. We apply these concepts in a defense scenario, modeled to analyze the loyal wingman concept, which we consider an interesting testbed for cooperative decision-making as well as low-level control techniques. The methodologies were merged with the creation of a 3D UAV simulator to provide an application and evaluation of behavior strategies and control methods.

© 2022 IEEE.This paper is concerned with the robust guidance and control of fully actuated mobile robots subject to velocity and control constraints in dynamic environments involving external disturbances. The overall method consists of an outer-loop guidance based on the acceleration-velocity-obstacles strategy and a stabilizing control loop based on a global sliding mode policy. The guidance strategy generates velocity commands aiming to reach a target position while avoiding collision with moving obstacles and respecting velocity and acceleration bounds. On the other hand, the global sliding mode ensures that the velocity commands are, in theory, exactly tracked all the time. The proposed method is numerically evaluated using two-dimensional robots and shows to be effective.

© 2022 IEEE.The present paper proposes a novel specified-time stable second-order sliding-mode dynamic system, formulated through a modification of the super-twisting algorithm. A broader definition of finite-time stability with specified convergence time, denominated here as specified-time stability, is provided. We devise a state observer for a damped simple pendulum to test the proposed algorithm's efficacy. The simulations illustrate that the estimation errors are taken to the origin at the specified settling time, with proper choice of the observer parameters.

© 2022 IEEE.This paper is concerned with the design of a predefined-time sliding mode control law suitable for the attitude control of a quadrotor aerial vehicle. Using the Newton-Euler approach, the modeling of the rotation kinematics and dynamics of the quadrotor is formulated in terms of the control errors and put in the regular state-space form. Then, a multi-input predefined-time first-order sliding mode control law is designed so that, under reasonable conditions, the settling-time bound of the tracking error can be directly specified by a unique parameter independently of the initial conditions. The proposed control law is evaluated through numerical simulations where the results have confirmed that the tracking errors in fact converge to zero within the predefined time.

© 2017 IEEE.The present work deals with the optimal control allocation of under-Actuated multirotor aerial vehicles (UAMAVs). The problem is formulated as a convex optimization, which unifies the previous methods and extends the literature by considering the rotors' dynamics and actual bounds. A feasibility analysis based on the control allocator admissible set is presented, which provides a condition for an exact control allocation to exist. This condition can be explicitly used in the design of the control law, thus improving its synergy with the control allocator. The proposed control allocation method is numerically exemplified on an octa-rotor UAMAV.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.The present work proposes to analyze the performance of five eddy-viscosity turbulence models in predicting an internal single-phase incompressible turbulent flow through an elbow pipe. Validation is achieved by comparison with LES and experimental benchmark results. Particular emphasis is placed in the study of the velocity fields under challenging conditions in terms of turbulence modeling. Ultimately, the analysis aims to determine the most adequate model among the analyzed ones in terms of accuracy, envisioning further application in multiphase flows. Results show that the SST closure is the most appropriate turbulence model to predict the velocity profile in regions of significant streamline curvature, whereas, in the presence of high adverse pressure gradients, the most appropriate one is the realizable k- ϵ model. Furthermore, a quantitative analysis suggests that a modification to the F1 blending function in the SST model may improve the mean velocity agreement with LES benchmark results in the near-wall region located downstream of the bend.

© 2022, Krishtel eMaging Solutions Private Limited.This paper is devoted to the reliability analysis of rotor-bearing systems, based on the combination of Kriging metamodels and the First-Order Reliability Method (FORM). The main motivation arises from the fact that high-fidelity structural models generally lead to high computation costs, which can be strongly alleviated using surrogate models. Since applications to rotating machines have not been sufficiently explored so far, the contribution of the present paper consists in the evaluation of the performance, both in terms of accuracy and computational effort, of a numerical strategy based on the combination of Kriging metamodels and FORM to this type of machines, accounting for their typical frequency domain responses and applicable limit-states. Such an evaluation is made by confronting four different strategies, combining: (i) full finite element models and Monte Carlo simulations; (ii) full finite element models and FORM; (iii) Kriging metamodels and Monte Carlo simulations; (iv) Kriging metamodels and FORM. Results show that the Kriging/FORM strategy provides substantial decrease of computation effort, while keeping satisfactory accuracy of reliability estimations. In addition, a procedure is proposed for improvement of the accuracy of Kriging/FORM reliability estimates, by enriching the Kriging design of experiments in the vicinity of the Most Probable Failure Point.

© 2022 Elsevier Masson SASConsidering that flutter represents a potential catastrophic event in the context of aerospace structures, numerous studies have evaluated a number of strategies to avoid and/or control this kind of aeroelastic phenomenon. Currently, both active and passive control have been investigated to prevent instabilities induced by the interaction between aerodynamic and structural forces. It is also important to highlight the successful cases in which passive control techniques using viscoelastic materials have been useful to mitigate several types of vibration problems. However, there are still opportunities to explore the potential of control using viscoelastic material in the scope of aeroelasticity, especially when involving its combination with other control techniques. Therefore, this work presents a strategy involving a hybrid approach to aeroelastic control of a simplified unswept and untapered wing, using a combination of passive and active techniques. Passive control is achieved by the use of viscoelastic materials inserted as resilient elements in the aeroelastic model, while active control is performed by means of the deflections of a flap-like aerodynamic control surface, governed by a proportional-derivative control law. The results show that the application of the passive control alone causes an increase of up to 25.4% in critical flutter speed. In addition, the association of passive and active controls lead to higher control performance and the critical speed is increased by a further 6.8%, thus providing a broader safe flight speed range. Hence, the investigation indicates that the hybrid control approach exploring viscoelastic materials can be advantageous in practical applications.

© 2021 IAAThe present study addresses the problem of automatic path planning of a manipulator-like spacecraft in orbit. Based on the concept of optimal control and off-line establishment of optimal trajectories, the study proposes a formulation of multiobjective optimization that accounts for multiple aspects of motion. The effect of manipulator mass is analyzed. Then, the effect of multiple objectives on the optimal path, such as the satellite displacement, arm manipulability and maximum torque, are evaluated. In addition, the end-effector positioning, avoidance of collision between the arm and the spacecraft, and minimization of torque requirements are considered as objectives to be minimized, subject to uncertainty inside the berthing box. The numerical procedure includes a machine learning strategy that is able to learn from both training data and mission tasks. It is used during inverse kinematics analysis, when the Cartesian position is the input parameter and the joint angle estimate is the output. This information improves the convergence rate of the optimization procedure, which leads to the precise value of the angle of the joint. The learning strategy is effective for estimating the solution when five or more samples are available, and the result is improved as new data is added to the analysis. The diversity of scenarios, metrics and parameters considered in the numerical experiments confirms the viability and robustness of the proposed methodology.

© 2021, Brazilian Society for Automatics--SBA.A comparative analysis of machine learning techniques for fault diagnosis of rotating machines based on images of vibration spectra is presented. The feature extraction of different types of faults, including unbalance, misalignment, shaft crack, rotor–stator rubbing, and hydrodynamic instability, is performed by processing spectral images of vibration orbits acquired during the machine run-up. The classifiers are trained with simulated data and tested with both simulated and experimental data. The latter are obtained from laboratory measurements performed on an rotor-disc system supported on hydrodynamic bearings. To generate the simulated data, a numerical model is developed using the finite element method. Deep learning, ensemble and traditional classification methods are evaluated. The ability of the methods to generalize the image classification is evaluated based on their performance in classifying experimental test patterns that were not used during training. The results of this research indicate that, despite considerable computational cost, the method based on convolutional neural networks presents the best performance.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.The objective of the present work is to discuss the effects of model enhancements on the capability of performing static aeroelastic analyses of aeronautical configurations. The model improvements addressed in this effort concern the use of finer aerodynamic grids, different turbulence models and the size of the modal base for the representation of the structural deflection solution. The study considers the NASA Common Research Model (CRM), from the 6th AIAA CFD Drag Prediction Workshop, and the High Reynolds Number Aerostructural Dynamics (HIRENASD) configuration, from the 1st AIAA Aeroelastic Prediction Workshop. A clear improvement in the aerodynamic prediction of drag, pitching moment and pressure coefficient distributions is observed for the NASA CRM case. For the HIRENASD test case, aerodynamic grid refinement has yielded results that demonstrate the robustness of the developed fluid-structure interaction process.

© 2023 Elsevier Inc. All rights reserved.Solar cells and photovoltaic devices are based overall on metal oxides and heterostructures. This is a technology in advance, with remarkable interest due to its low impact on the environment in comparison to the most used forms of energy conversion. Additionally, the oxides are most abundant, easy, and less expensive to obtain compared to other materials for such applications. Although the metal oxide–based photovoltaic devices show, usually, low conversion efficiency, some studies have shown capable of obtaining PCE higher than 10% or 20% using enhanced heterostructures. This chapter presented a review of the state of the art of metal oxide heterostructures applied mainly in photovoltaic devices and solar cells. A special focus is given to studies related to some of the most applied materials, such as ZnO, ZnO:Al, (AZO), and TiO2, and to heterostructures based on metallic oxides of copper, zinc, magnesium, vanadium, etc.

© 2022 Universidade Federal de Sao Carlos. All rights reserved.This work reports the properties of GaN films grown onto c-Si (100) at relatively low substrate temperature (400°C) by reactive magnetron sputtering. The study depicts the effect of working pressure and RF power on the GaN film structural, vibrational and optical properties characterized by X-ray diffraction, atomic force and scanning electron microscopies, Raman spectroscopy and spectroscopic ellipsometry. Unusual low pressure deposition condition (0.40 Pa) was achieved by using a separated argon inlet directed to the Ga target surface, resulting in improved crystalline quality of the films. In this condition, the preferential crystalline orientation, the surface morphology and the optical gap of the GaN films show a strong dependence on the RF power applied to the Ga target, where low RF power (30-60 W) was responsible for increasing the c-axis orientation and the optical gap, while higher RF power (75-90 W) decreased the overall crystal quality and increased the surface roughness.

© 2021 Author(s).The influence of the oxygen gas supply on the stoichiometry, structure, and orientation texture of polycrystalline cobalt oxide films was investigated in this study. The films were grown by direct current reactive magnetron sputtering using a metallic Co target and different O2 inlet flow rates (0.5-5.0 SCCM). The deposition power (80 W), the argon gas flow (40 SCCM), and the total working pressure (0.67 Pa) were kept constant during depositions. The results evidence a strong influence of the oxygen flow over the film's stoichiometry and structure, where low oxygen flows (<2.0 SCCM) favor the formation of the rock salt CoO phase while higher oxygen flows (>2.5 SCCM) favor the spinel Co3O4 phase formation. The coexistence of monoxide and tetraoxide phases is only observed for the 2.5 SCCM oxygen flow condition. Strain effects related to the oxygen partial pressure are also observed and discussed. Computer simulations of the reactive sputtering growth supported the analysis of the film properties and its correlation to the oxygen partial pressure.

© 2022 The Authors.The nonlinear thermophysical properties significantly affect the temperature field and the appearance of the weld bead in the LASER Beam Welding (LBW). Then, it is vital to have a well-defined numerical model for analyzing the thermal behavior of the welded material. Nonetheless, many papers still address the welding simulation using constant thermal properties. In this way, this paper proposes a three-dimensional thermal analysis of an unsteady LBW aiming to compare the difference between the constant and nonlinear thermophysical properties approaches. It applied the Finite Volume Method (FVM) to solve the nonlinear three-dimensional heat diffusion equation with an enthalpy function to model the phase change using a fully implicit scheme. In traditional models, these considerations promote a significant increase in computational time for the convergence of the method. Thus, CUDA-C in-house parallel routines were implemented and executed in a Graphics Processing Unit (GPU) to solve this problem. Lab-controlled experiments validated the proposed methodology. The results highlighted the importance of using the nonlinear approach. Furthermore, a detailed study demonstrated the difficulty of knowing precisely the placement of thermocouples, given the high-temperature gradient in the welding processes. The proposed methodology demonstrated to be a faster, cheaper, and efficient way to simulate the LBW.

© 2022, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.In welding processes, many factors contribute in achieving a required quality of the welds. Those factors are numerous and they may interact with each other, affecting response parameters such as welding penetration and the heat-affected zone (HAZ) size. Some factors are more important while the influence of others is negligible. To find an optimum factor combination in order to maximize penetration and minimize the HAZ is not an easy task. This contribution is aimed to evaluate the influence of welding energy (E) versus the influence of current (I) and welding speed (Vw) on the penetration and HAZ volume in the autogenous tungsten inert gas welding process. For this purpose, two numerical models are proposed. The first considers an in-house finite volume numerical model, and the second is based on response surface method. A sensitivity analysis of the proposed numerical model using two strategies is also performed. In addition, to determine the best-operating conditions, a multi-objective optimization problem is proposed and solved. The presented numerical models were found to provide good concordance in terms of coefficient of determination and p-value, indicating its significance. Each model (with one or more independent variables) represents detailed information about the physical process and can be used for optimization. The sensitivity analysis demonstrates that the current affects penetration and HAZ volume much stronger than the welding speed does. Physically, this is due to the fact that the current has linear (arc coupling) and non-linear (Joule effect and pressure gradient) influence, and the welding speed contributes linearly, modulating the heat conduction. Finally, it was demonstrated a compromise between the penetration and the HAZ volume by addressing multi-objective optimization. In this context, point C (I = 250 A; Vw = 24.8 cm/min) of the Pareto curve is the optimal option for operation since it provides a lower relative HAZ volume while keeping the same penetration and higher productivity (welding speed).

© 2022, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.In aeronautical manufacturing, the assembly of large structures like wings and fuselages usually uses riveting to join the primary parts. The riveting process induces deformations between parts that affect aircraft performance and increase manufacturing costs. In this work, a finite element analysis of a rivet installation is developed to predict the induce deformations as a tool for the design of the assembly process in aeronautical industry. Different from the existing literature, which focuses mainly on fatigue analysis, the method presented in this paper focuses on finding a solution for determining induced deformations that can be applicable, from an industrial perspective, to aircraft production lines. A 2D axisymmetric model represents the installation of a single rivet joining two metal sheets with a force-controlled squeezing. The simplified model is proposed to reduce computational costs. An adaptive meshing scheme is adopted to better describe the forming of the driven head and improve the accuracy of the model. When comparing with existing methods, this attribute allows to better predict the profile of the radial expansion along the thickness of the sheets because the mesh is recalculated at each iteration to prevent distorted elements. Up to 18% relative difference was observed between the mesh with and without adaptive scheme. The results indicate that the radial expansion in the rivet hole is directly related to the squeeze force. An uneven expansion occurs through the thickness of the sheets indicating bending of the material. The mean radial expansion at half-pitch of 4 diameters was used to estimate the radial expansion of a rivet line composed of two or more rivets. The obtained results show that, for a rivet line composed of 50 rivets with a 4-diameter pitch (a panel with 952.5-mm length) the mean radial expansion for a 27.4-kN squeeze force is of 0.5 mm. It was also observed that the inner sheet (closest to the driven head) expands at least three times more than the outer sheet, indicating a bending mechanism is present in the panel.

© 2021This work presents a novel approach for visual servoing of robotized aerospace manufacturing cells, based on the combined use of a camera and a 2D-beam scanner and a 1-D beam distance sensor attached to the end-effector of a collaborative robot. The proposed system can detect features associated with mechanical bounds over the aircraft structure, making possible the robot automatic online trajectory/path generation when the robot performs a target task over an aeronautical part. The effectiveness of this method is demonstrated by means of experimental evaluations carried out in unstructured environments without illumination and temperature control (simulating real shop floor conditions), evincing that the proposed approach is more robust. We also show that it is able to automatically generate and follow a target path with an accuracy of 0.40 mm and repeatability of 0.59 mm, which is roughly 2 times more accurate than the classical computer vision servoing used in the experiments. The proposed solution is suitable to applications in modern collaborative robotized aerospace assembly cells.

© 2022 ESREL2022 Organizers. Published by Research Publishing, Singapore.Air transport demand for patients increased significantly in Brazil during the COVID-19 pandemic. This occurred because hospitals were overcrowded in some regions, and patients needed to be moved over the country’s continental distances. The transport of patients with infectious diseases leads to an increased crew’s mental and physical overload due to the care provided to critically ill patients, utilization of complete personal protective equipment, and fear of contamination. To assess the mental workload levels under these conditions, health professionals involved with the air transport of patients with COVID-19 from the Brazilian Air Force were asked to answer questionnaires about flight missions performed, the patients’ clinical status, and the NASA-TLX questionnaire. Nine healthcare professionals participated in the survey. The NASA-TLX questionnaire’s outcomes were analyzed and compared according to transport time, the number of patients transported, and the patient’s clinical status. Transport with unstable patients showed the highest final weighted rating, and the most significant NASA-TLX dimensions were mental demand and reported frustration.

© 2022, International Council of the Aeronautical Sciences. All rights reserved.Helicopter rocket-firing requires continuous pilot training for mission accomplishment purposes, so measuring the mental workload involved could help to improve training effectiveness and flight safety. Physiological and flight data from two Brazilian Army pilots with distinct experience levels have shown that the aiming phase is the more mental demand, and some physiological patterns were identified. Pearson’s Correlation and Principal Component analysis, including shot stability parameters (aiming path area, perimeter, and deviation of maneuver parameters) and physiological data, have identified electrodermal activation as the more consistent human dimension related to the shooting performance.

© 2022 ICAS. All Rights Reserved.The HMI-HUFLab project is a joint Brazilian Swedish initiative in the area of human factors and design of human machine interfaces for future military concepts in Aeronautics. This paper gives a short introduction to this Brazilian Swedish collaboration. It describes the main challenges for setting up the bilateral collaboration and how challenges were tackled. We present the first projects results, which includes the definition of relevant context and scenarios for the future air domain, a review of literature and implementation of complementary simulation environments in both countries.

© 2022 ICAS. All Rights Reserved.Helicopter rocket-firing requires continuous pilot training for mission accomplishment purposes, so measuring the mental workload involved could help to improve training effectiveness and flight safety. Physiological and flight data from two Brazilian Army pilots with distinct experience levels have shown that the aiming phase is the more mental demand, and some physiological patterns were identified. Pearson's Correlation and Principal Component analysis, including shot stability parameters (aiming path area, perimeter, and deviation of maneuver parameters) and physiological data, have identified electrodermal activation as the more consistent human dimension related to the shooting performance.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.In this paper the creation and maintenance of a bilateral network is presented. Sweden and Brazil have a long standing relation stretching far beyond aeronautics. However, it was intensified with the acquisition of the Swedish Saab Gripen combat aircraft for the Brazilian Air force. This led to an intense build-up of industrial collaboration and in the wake of this, also a bilateral academic network was formed to both take advantage of this, as well as support the process and encourage spin-off effects to other parts of society. To be sustainable it is argued that a network needs the right support and encouragement to be able to grow organically in a sustainable way, based on personal relations. Once this is in place, an academic bilateral network can be formed that can be maintained effectively over time at a low cost.

© 2022 ICAS. All Rights Reserved.The problem addressed in this research is the control of a remotely piloted aircraft using a satellite communication link with communication delay. To investigate the problem, it was necessary to build and investigate a test platform where the pilot could land an aircraft outside the standard operating area. The mission mandatorily depends on communication via satellite. The dynamic model of the aircraft used for the experiment was developed in the Matlab/Simulink software, with all inertial and aerodynamic modeling arrangements. The graphical interface for displaying the scenery, 3D model of the aircraft, and items used during the experiment are generated in the FlightGear software. The Unity software is used to develop a secondary interface that receives data from Matlab/Simulink. All tests studied were monitored through performance measurements, concerning deviations from the expected trajectory, using physiological sensors. The experimental data are processed to evaluate the influence of the predictive interface during flights performed with delay in the visualization.

© 2022 ICAS. All Rights Reserved.Safety-II assumes that individuals and organizations habitually adjust their performance to match current demands, resources, and constraints to compensate the incompleteness of procedures and instructions. It suggests that everything happens basically in the same way, regardless of the outcome. This work aims to analyze the aircraft touchdown procedure through this perspective, focusing on the everyday performance and the consequent variability. The Functional Resonance Analysis Method or FRAM provides a way to explain outcomes using the idea of resonance - an activity is described through a pool of functions and the outcomes arise from their day-by-day variability. To characterize the functions' variability, Flight Data Monitoring (FDM) techniques are here used. To examine specific instantiations of the model and understand how the potential variability of each function can become resonant, the application of Monte Carlo Simulation (MCS) is proposed. To apply the MCS, a linear regression is performed in order to capture the relationship between the functions' outputs and their inputs. This method is applied to the touchdown of 288 flights. The outcome is a model to assess the risk of a long touchdown of the current sample, including the organizational, human, and technological aspects of the complex aeronautical system. Note that long touchdown is a runway overrun precursor.

© 2022 IEEE.The primary cost driver for the assembly of airframes is rooted in drilling, countersinking, and installation of fasteners. Customized automated systems, such as drilling machines and robotic platforms, are designed and built to perform these assembly processes. The operator is the closest individual to the automated system that influences its success. In addition, equipment operators must deliver quality parts within a specified cycle time in these long and repetitive processes. This work evaluates the workload of equipment operators of automated drilling processes for aerospace structures. The evaluation is carried out with experienced machine operators who work full-time in these automated drilling processes. Two different automated drilling processes are evaluated: robotic platforms and automatic drilling machines. This work evaluates workload in the different phases of the automated drilling process. This evaluation identifies phases where workload under-arousal and over-arousal may be present. Finally, recommendations to enhance human performance in automated drilling processes are presented. These results may be successfully used to improve the design of automated drilling machines and drilling processes for aerospace structures.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.The use of CubeSats is increasing to a wide range of areas in science and technology with some of them requiring an accurate Attitude Determination and Control System (ADCS) and deployable structures such as booms. However, small satellites commonly do not have latching systems to lock their booms, which introduce vibrations and oscillations and might degrade the ADCS performance. Also, some applications propose missions with CubeSats operating in close proximity and coordination, requiring thrusters to perform orbit maneuvers such as the planned ITASAT-2 spacecraft formation flying mission, which will have non-latching booms and a thruster. These thrusters can excite the satellite’s non-latching flexible booms, intensifying their impact on the ADCS. Additionally, on-off thrusters are usually controlled using a Pulse-Width Modulation (PWM), introducing more effects in the system’s dynamic. Hence, motivated by the ITASAT-2 mission, this work aims to understand the impact of a thruster’s PWM parameters in the non-latching flexible booms dynamics. Also, this work presents a framework to obtain the influence of PWM parameters on a satellite, which can be applied to other small spacecraft. The results show that booms’ deformation decreases when the thruster provides a continuous force, compared to a modulated force. Peaks in deformation and rotation were identified near frequencies of the non-latching flexible booms’ system. Further, it was verified that resonances might occur in latched booms at distinct PWM periods. Moreover, the influence of the non-latching mechanism and PWM parameters was observed in the system forming regions of larger deformation.

© American Society for Engineering Education, 2022.Federal grants have been supporting many Brazilian engineering master's students. The availability of these grants is dwindling, so universities on one hand and master's candidates on the other have been looking for alternatives to obtain master's degrees with less grant dependence/support. On the technical university side, this led to the emergence of options to start a master's program in the last semesters of the typical 10-semester undergraduate program. From the university's side and from the student's side it is interesting that such integrated effort is time and resource-efficient. To support this, at Instituto Tecnológico de Aeronáutica (ITA), a new Complementary Training Program (CTP) in Control and Automation Engineering was started in August 2021, serving mainly Mechanical, Electrical, Aeronautical, and Computer Engineering students. The standard goal of CTPs in Brazil is to extend the major undergraduate training in a similar way as a US minor does. Thus, the baseline purpose of the new program is to provide undergraduate students with a complementary education, transversal to engineering courses, which enables them to work as Control and Automation engineers, without the need for training supplementation after graduation. However, by offering a well-designed course choice, this program will also allow for: (a) extending the scope of undergraduate studies, and (b) deepening specific topics that are already part of the undergraduate curriculum. In the scope of the Institute's undergraduate and master's degree integration initiative, this second particularity (item b) may yield anticipated credits for a master's program. Specific features of the program may further benefit students aiming at a master's degree. This paper details the structure of the CTP and the gains expected in terms of incentives for the Institute's Mechanical-Aeronautical Engineering as well as the Electronics and Computer Engineering Master's Programs.

© 2021 Elsevier Masson SASThe Scintillation Prediction Observations Research Task (SPORT) nanosatellite is being developed in partnership with the National Aeronautics and Space Administration agency and the Brazilian Space Agency, with its launch planned for 2022. Its goal is to collect data to improve our understanding of plasma bubbles and the condition that lead to their formation, helping to predict and mitigate their interference in navigation and communication systems. Therefore, to reach this goal, the satellite has several scientific instruments to perform in-situ measurements, with five of them positioned on four booms. These booms do not have a latching system to lock their position; instead, torsional springs are employed to keep them in the deployed state, holding them against their mechanism's structure. This configuration of torsional spring and collision may lead to vibration with the potential to degrade the Attitude Determination and Control System performance, impacting the whole mission. Motivated by the lack of literature covering the non-latching booms dynamics in satellites, this work proposes a framework based on multibody dynamics to simulate satellites with such booms. It also presents a practical method to acquire experimental data and identify the parameters of the booms' deployment mechanism. Later, this work applies the proposed framework and investigates the impact of non-latching booms on the satellite control system to verify if SPORT is able to complete the maneuver. Therefore, experiments were conducted to calibrate both spring and collision models. The multibody model of the satellite was developed and later validated using commercial software. The method for capturing booms' data and determining the mechanisms' parameters shows a satisfactory performance near the booms' deployment position. The proposed framework to simulate satellites with non-latching booms is applied to the SPORT satellite. Simulations in closed-loop indicate that the booms' influence on the SPORT's control system is negligible and the satellite meets its requirements.

© Proceedings of the International Forum of Aeroelasticity and Structural Dynamics 2022, IFASD 2022.As economic and environmental requirements surge, aircraft manufacturers incorporate a myriad of features in aircraft design aiming to reduce fuel consumption. One endeavor to increase fuel efficiency is related to increasing wing aspect-ratios, improving the aerodynamic efficiency of wings. Even though high aspect-ratio wings contribute to improving aircraft fuel efficiency, these slender wings present high structural flexibility, undergoing large deflections under operational loads. In this case, conventional linear structural analysis fails to predict accurate structural results. Then, nonlinear structural analysis needs to be employed for properly capturing the static aeroelastic response of such wings. In this context, this work proposes a fluid-structure interaction methodology coupling a full-potential aerodynamics solver with a nonlinear structural solver to evaluate the static aeroelastic behavior of very flexible wings. The methodology is applied to the Pazy Wing, a very flexible rectangular wing, as part of an international cooperation in NASA’s Aeroelastic Prediction Workshop 3. Comparisons between simulation and wind tunnel test results found in the literature are used for validating the developed methodology. Further, the work seeks to capture deviations in the wing deformed shape and aerodynamic loading when linear and nonlinear structural models are employed in the aerostructural scheme.

© Proceedings of the International Forum of Aeroelasticity and Structural Dynamics 2022, IFASD 2022.This paper presents a static aeroelastic investigation of the rolling capability of a modern flexible wing with the objective of flight test campaign clearance. A conventional configuration transport aircraft was evaluated in transonic conditions between Mach 0.82 and 0.89. A fluid-structure interaction tool with aileron deflection was considered to simulate the wing flight deformed shape effect on rolling capability, also with the undeformed fluid dynamics simulation reference for comparison. The applied code E2-FSI, which couples Reynolds Average Navier Stokes (RANS) fluid dynamics and static structural analysis, was improved to consider the different positions of control surface. The numerical results were compared to wind tunnel test data, with and without linearized aeroelastic corrections. The comparison in terms of rolling coefficient and flow topology are presented. The improve in the method fidelity resulted in advanced understanding of extreme rolling condition.

© 2022 Elsevier B.V.Polyaniline (PAni) widely studied conductive polymer due to its incredible versatility, electrical properties, and low cost. PAni usually is produced by chemical or electrochemical synthesis. However, these processes either generate a large amount of waste or are expensive and produce a small amount. The catalytic system incorporated into the PAni synthesis can be a strategic way to develop clean and low-cost processes. Therefore, we propose a synthesis of PAni catalyzed by carbon fiber (CF) reported for the first time. The procedure is to immerse the CF in an aqueous solution of aniline and H2SO4, at room temperature, in an open flask. Tests were carried out to investigate the CF as a catalyst and the molecular oxygen as an oxidant in the polymerization reaction. The samples were characterized by scanning electron microscopy, Raman spectroscopy, infrared spectroscopy, and X-ray photoelectron spectroscopy. According to the analyses, the reaction catalysts are heteroatoms on the fiber surface. Molecular oxygen present in atmospheric air is the oxidant of the reaction. The method is environmentally friendly, simple, and economical route to produce a conductive form of PAni on carbon fiber. The composite produced was evaluated as a possible electrode for a supercapacitor, and presented interesting results for application in energy storage devices.

© 2022 by the authors.Soft reliner and glaze are materials used over full or partial dental prosthesis to prevent excessive pressure on the supporting tissues. They are also indicated as supportive treatment for dental stomatitis, especially when modified by the addition of medications. The objective of the work was to evaluate the antimicrobial effect of silver-coated silica nanoparticles in a glaze and a soft reliner. The nanoparticles were synthesized, characterized, and tested by minimum inhibitory concentration (MIC) for C. albicans SC5314. Then, the nanoparticles were incorporated to a glaze and a soft reliner, which were called nanocomposites. Then, the nanocomposites were divided into six groups (n = 12): CG: glaze/reliner; CR: reliner; G1: glaze + 1% nanoparticles/reliner; G2: glaze + 2.5% nanoparticles/reliner; R1: reliner + 1%; R2: reliner + 2.5%. The nanocomposites were characterized by a goniometer and by a scanning electron microscope. The antibiofilm test was performed against C. albicans SC5314. According to the MIC results, the non-functionalized nanoparticles reduced fungal growth at 1000 μg/mL and the functionalized nanoparticles at 2000 μg/mL. The functionalized nanoparticle had a superior dispersion being selected for the antibiofilm test. There was a reduction of 64% in CFU/specimen count for the glaze, not statistically significant (p = 0.244). For the soft reliner, there was an increase in CFU/specimen with the presence of nanoparticles, still not statistically significant (p = 0.264). In conclusion, it is necessary to conduct new studies to increase the release of silver, thus improving nanoparticles’ antifungal potential.

© 2022, The Polymer Society, Taipei.The integration of biomaterials in tissue regeneration has been showing effectiveness in the treatment of diseases related to bone structure and tissue repair. Membranes have aroused interest due to their ease of manufacture, variation in composition, and the structure of the biomaterial. The incorporation of bioactive glass (BG) increases bioactivity, and when doped with therapeutic ions, changes in the physical-chemical composition of the biomaterial are expected to enhance its biological effect. This study aimed to produce polycaprolactone (PCL) membranes incorporated with 58S bioactive glass, doped with Zinc (Zn) by the electrospinning technique, and evaluate the influence of this biomaterial in the activity and differentiation of mesenchymal stem cells. The BG was produced by using the sol-gel process; next, before the PCL preparation, the BG was doped with zinc in a solution. Then, PCL solutions were prepared with 7% by weight of BG and doped with 10% ZnCl2. Afterward, the electrospinning process was carried out using the fixed parameters: 2mLh-1 flow rate, 10kV voltage, and 12cm distance. Before the biological assays, the chemical elements present in the fibers were evaluated by energy dispersion X-ray spectroscopy (EDS), and the mapping technique. The morphology of the biomaterial and the diameter of fibers were analyzed by scanning electron microscopy (SEM), and the hydrophilicity of the membranes was evaluated by the contact angle technique. The in vitro tests consisted of cell plating with mesenchymal stem cells (MSC’s), previously obtained from rat femurs, at a density of 1x104 per well that contained three different groups: a) P: mesenchymal stem cells plated with PCL; b) PB: mesenchymal stem cells plated with the composite of PCL / BG; c) PBZ: mesenchymal stem cells plated with the Zn doped PCL / BG composite. To evaluate the influence of the biomaterial on osteoblastic activity and differentiation, osteogenic and non-osteogenic media were used in tests of cell viability (MTT assay), total protein content, alkaline phosphatase activity (ALP), and mineralization nodules. The analysis by SEM proved that the electrospinning technique was efficient for producing fibers incorporated with bioactive glass, and EDS and the mapping technique confirmed the chemical components of each group of fibers, including the doped zinc in the bioactive glass. The analysis of fibers diameter showed that P and PBZ had presented fibers with a larger diameter than the PB group, and the contact angle technique showed an increase in the hydrophilicity of the group containing doped Zinc when compared to the other groups analyzed. The MTT assay confirmed that the membranes weren´t cytotoxic and allowed cell viability, total protein content showed that all the groups had cell activity, with a statistically significant difference between the groups (p<0,05). Even with no statistically significant difference, osteogenesis was proved by ALP activity and the formation of mineralization nodules. Based on the results, the PCL membranes incorporated with 58S bioactive glass doped with zinc have shown promise in tissue engineering for use in bone tissue regeneration.

© 2022, Universidade Estadual Paulista, Institute of Science and Technology of Sao Jose dos Campos. All rights reserved.Objective: Thermally activated acrylic resins (RAATs) are widely used in dentures as a base material due to their good dimensional stability and biocompatibility. However, their low thermal conductivity is a disadvantage, as it affects acceptance when using dental prostheses. Thus, the objective of this work was to measure the conduction heat in RAATs with and without incorporation of silica and silver nanoparticles (NP) and rigid reline (RR). Material and Methods: For this, samples were made and divided into 10 groups (n = 6). The first five groups were 2-mm-thick samples: G1 (RAAT control), G2 (RAAT + RR control), G3 (RAAT and NP + RR), G4 (RAAT + RR and NP), and G5 (RAAT and RR modified by NP). In the other five groups, 8-mm-thick samples were made: G6 (RAAT control), G7 (RAAT + RR control), G8 (RAAT and NP + RR), G9 (RAAT + RR and NP), and G10 (RAAT and RR modified by NP). The heat that cross the surface of the specimens was quantified using a wireless device. The data were submitted to two-factor ANOVA statistical analysis and Tukey´s test with a 5% significance level. Results: After measuring the temperature variation as a function of time, it can be observed that there was a statistically significant difference for thermal conduction between the control groups and those modified with NP. Conclusion: Thus, it was possible to conclude that the NP improved the heat conduction in RAAT and in the RR because the nanoparticles have a higher thermal conductivity.

© 2022 Elsevier B.V.Recently, the release of antibiotics, such as sulfonamides, into the environment has raised significant concern due to the potential creation of antibiotic-resistant bacteria. Thus, the development of remediation technologies for effluents containing such compounds is of utmost urgency. In this context, this work evaluated the creation of a resorcinol-based carbon xerogel/zinc oxide photocatalyst (XC/ZnO) to efficiently promote the photodegradation of the antibiotic known as sulfamerazine in aqueous media. The employment of this carbonaceous structure as a co-catalyst is justified by its high surface area and electrical conductivity. The methodology used in the synthesis of the composites was a simple one-pot reaction, combining the simultaneous precipitation of zinc oxide and polycondensation of the resorcinol-based carbon gel. Regarding the composites' characterization, X-ray diffractometry confirms that the composites have the Wurtzite structure of the zinc oxide, whereas the carbon xerogel formation is evidenced by the infrared, diffuse reflectance, and X-ray photoelectron spectroscopies. Morphology-wise, the XC/ZnO is arranged as nodular particle agglomerates, with particles between 500 nm and 50 nm. The photocatalytic tests under simulated solar radiation show that the composites developed are superior to the pure oxide in the photodegradation of sulfamerazine, as all XC/ZnO materials developed achieved higher apparent reaction rate constants (kapp) than pure zinc oxide, with the XC/ZnO 0.5 material obtaining a kapp 75% higher than the one observed for the ZnO sample. Furthermore, the chronoamperometry tests confirmed that the optimized composite (XC/ZnO 0.5) has a greater capacity for photocurrent generation when compared to pure zinc oxide. Therefore, the modification proposed was successful to enhance the photodegradation of sulfamerazine in aqueous media, highlighting the viability of the composites developed for photocatalytic applications.

© 2021, Korean Society for Precision Engineering.Powder metallurgy represents an alternative to increase sustainability in the manufacturing of automotive gears, but its potential is hindered by a certain lack of knowledge on surface integrity properties that can impair the gear performance. This study explores the effects of the microstructural differences induced by this chain on the residual stress heterogeneity state of gears. X-ray diffraction methods of macro residual stress mapping and line profile analysis were applied for measurements of gear teeth after subsequent steps of the powder metallurgy and the conventional wrought steel chains. The powder metallurgy chain induced more pronounced heterogeneities than the conventional manufacturing, characterized by non-uniform residual stress distributions along the lead and the involute profiles of gear flanks. These non-uniformities observed after carburizing were traced back to the previous steps, surface densification, sintering and compaction. The residual stress distribution patterns of these steps were compatible with the plasticity dynamics of each manufacturing process. Such surface integrity heterogeneities result in a residual stress gradient along the gears functional surface, exposing particular regions to be more susceptible to fatigue effects.

© BME-PT.Porous polymeric scaffolds provide a physical substrate for cells to attach and proliferate, allowing the formation of new tissue. These materials are broadly used in the tissue engineering field due to their ability to mimic native tissue. Each application requires specific morphologies and resistance, among other several features. To accomplish these requirements, various techniques are available, each one with its advantages and disadvantages. Among the most relevant techniques are salt leaching, solvent casting, gas foaming, thermally induced phase separation, freeze-drying, electrospinning, thermally induced self-agglomeration, and three-dimensional (3D) printing. In this review, a brief and simple explanation of each method is described, along with some recent results and each technique’s advantages and disadvantages. It is expected that this review will bring important guidance in the production of polymer scaffolds for tissue engineering.

© 2022 Elsevier LtdAs the new space era advances, there is an increasing demand for long-term missions beyond Earth's orbit, such as on Mars and the Moon. The level of complexity of these missions is higher than conventional missions in terms of duration, particularly the energy demand required. To become viable, power generation systems must have a high power density, that is, high power associated with low mass. From this perspective, dynamic nuclear power generation systems coupled with electric propulsion are considered the most promising systems for deep-space exploration and colonization missions. Thus, to provide valuable information for the development of a dynamic energy conversion system for space, this study carried out thermodynamic modeling of a nuclear-powered Stirling cycle coupled with a dynamic engine model for space purposes. By means of numerical modeling, the constructive parameters of the Stirling engine, such as regenerator efficiency, compression ratio, heat exchanger thermal conductance, engine frequency, piston stroke, and area, are varied to understand the impact of these parameters on the final system performance. The results show that the regenerator efficiency can provide significant gains in the engine efficiency. However, a very high regenerator efficiency reduces the power of the cycle. The engine compression ratio tends to increase the engine efficiency, but a compression ratio above six provides marginal gains for cycle efficiency. From the results obtained, the best parameters yielded a system with a power output of 260.5 kW and a power density of 35.38 kg∙kW-1. This study can serve as a theoretical guideline for the future design of nuclear-powered Stirling engines for space applications, providing insight into the constructive parameters that influence the overall performance of the system.

© 2021 Elsevier LtdIn recent years, the interest of space agencies and private companies in space exploration has increased, mainly in deep space missions. This type of mission poses great challenges due to the high energy level demanded from the power systems, requiring a more efficient and compact energy conversion system. Thus, this work carried out a finite-time thermodynamic model and exergy analysis of a Stirling cycle for nuclear space power generation. The thermodynamic model was coupled to a simple dynamic Stirling engine model and takes into account several aspects such as the thermal losses between the hot and cold side of the Stirling cycle, finite-time regeneration, temperature drop along heat pipes, and variable compression ratio. The system performance and component irreversibilities were evaluated by varying the nuclear core temperature and the cold side temperature of the cycle. Then, the figure of merit mass per power output (kg.kW-1) of the energy conversion system was computed, enabling the model to find temperature conditions for a system that aligns high efficiency and compactness. The results showed that the component with the greatest irreversibility is the reactor core with a value of 496.14 kJ, representing 68.18% of the total irreversibility. The exergy analysis showed that only 5.15% of the total exergy is used for power generation and 24.33% is rejected to space. Moreover, the cold side temperature of 352 K provided the system with the lowest value of mass per power output (87.69 kg.kW-1).

© 2021 Elsevier LtdScramjet (supersonic combustion ramjet) engines are often seen as a promising alternative to place payloads in the Earth's orbit. Such air-breathing engines have a simple structure and few moving parts. On the other hand, high heat fluxes and pressure loads on the walls, shock-wave-boundary-layer interactions, and the risk of choked flow inside the isolator channel are a few examples of obstacles that need to be addressed during scramjet design. Therefore, this study aims to evaluate of different air freestream conditions on the flow field in a scramjet inlet (compression ramps and isolator) through detailed three-dimensional computational fluid dynamics (CFD) simulations. The Mach number, flight altitude, and angle of attack were the evaluated conditions. Moreover, this study also focuses on the behavior of the boundary layer separation located at the compression ramp corners, isolator entrance, and scramjet sidewalls. Regarding the Mach number variation, the results showed that high Mach numbers yielded high-pressure levels throughout the engine. Furthermore, a higher altitude promoted a lower total pressure field. Considering the angle of attack changes, it is evident that a higher angle of attack results in a decrease in airflow pressure, while an increase in the total pressure along the walls is observed. By investigating these freestream parameters, this work can contribute to the early phase of engine design, avoiding critical failures in the scramjet structure due to aerodynamic load and thermal stress.

© 2022 Elsevier LtdAs the new space era advances, there is an increasing demand for long-term missions beyond Earth's orbit, such as on Mars and the Moon. The level of complexity of these missions is higher than conventional missions in terms of duration, particularly the energy demand required. To become viable, power generation systems must have a high power density, that is, high power associated with low mass. From this perspective, dynamic nuclear power generation systems coupled with electric propulsion are considered the most promising systems for deep-space exploration and colonization missions. Thus, to provide valuable information for the development of a dynamic energy conversion system for space, this study carried out thermodynamic modeling of a nuclear-powered Stirling cycle coupled with a dynamic engine model for space purposes. By means of numerical modeling, the constructive parameters of the Stirling engine, such as regenerator efficiency, compression ratio, heat exchanger thermal conductance, engine frequency, piston stroke, and area, are varied to understand the impact of these parameters on the final system performance. The results show that the regenerator efficiency can provide significant gains in the engine efficiency. However, a very high regenerator efficiency reduces the power of the cycle. The engine compression ratio tends to increase the engine efficiency, but a compression ratio above six provides marginal gains for cycle efficiency. From the results obtained, the best parameters yielded a system with a power output of 260.5 kW and a power density of 35.38 kg∙kW-1. This study can serve as a theoretical guideline for the future design of nuclear-powered Stirling engines for space applications, providing insight into the constructive parameters that influence the overall performance of the system.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.For a long time, thermal power plants play important roles in world electricity and are expected to continue, at least, in the next decades. However, the finitude of fossil fuel sources leads to the crucial need for improving the existing power generation systems. In this study, an in-house computational code was developed and validated to evaluate the energy, exergy and economic performance for thermal power plants applications. Based on operating data of an actual lignite coal-fired steam power plant, two cycles were designed and compared. In the cycle in which more components were added, the fuel consumption was 9.44% lower to produce the same amount of power, making more effective use of the fuel resource. This substantial reduction in fuel consumption reflected lower electricity average costs for this plant. Comparing to the electricity price of a country using the same type of fuel, it was found that it could be lower by 1.62 percentage points for household consumers. Although the higher costs with capital investment and operational and maintenance (O&M) due to the addition of these components, the attractive economic performance of the cycle reduces the annual fuel costs and offsets the increase in capital and O&M costs.

© 2022 IEEE.This paper presents a study of the thermophysical properties of electric motors and of the structure of the robots used by ITAndroids' Very Small Size (VSS) team. To perform the modeling of the robot structure, the General Lumped Capacitance Analysis was used, assuming that the motor's internal temperature can be considered approximately uniform. This hypothesis was validated by means of Biot's Number, and the heat source term was evaluated in order to define which energy dissipation sources would be considered in the modeling. The obtained model was evaluated through numerical simulations to analyze the motors' temperature profile for different current values. We compared the obtained results with similar experiments found in the literature, concluding that the model could predict the system's behavior in a satisfactory manner. Therefore, this work contributes to the research area by providing a model able to predict the temperature of the electric motor under different workloads, thus, allowing the team to anticipate its overheating and prevent its premature burnout.

© 2021 Elsevier LtdIn recent years, the interest of space agencies and private companies in space exploration has increased, mainly in deep space missions. This type of mission poses great challenges due to the high energy level demanded from the power systems, requiring a more efficient and compact energy conversion system. Thus, this work carried out a finite-time thermodynamic model and exergy analysis of a Stirling cycle for nuclear space power generation. The thermodynamic model was coupled to a simple dynamic Stirling engine model and takes into account several aspects such as the thermal losses between the hot and cold side of the Stirling cycle, finite-time regeneration, temperature drop along heat pipes, and variable compression ratio. The system performance and component irreversibilities were evaluated by varying the nuclear core temperature and the cold side temperature of the cycle. Then, the figure of merit mass per power output (kg.kW-1) of the energy conversion system was computed, enabling the model to find temperature conditions for a system that aligns high efficiency and compactness. The results showed that the component with the greatest irreversibility is the reactor core with a value of 496.14 kJ, representing 68.18% of the total irreversibility. The exergy analysis showed that only 5.15% of the total exergy is used for power generation and 24.33% is rejected to space. Moreover, the cold side temperature of 352 K provided the system with the lowest value of mass per power output (87.69 kg.kW-1).

© 2022 ESREL2022 Organizers. Published by Research Publishing, Singapore.Health specialists deal with unsafe situations that are conducive to health risks, including the pressures and demands of the practice itself and the full situation of the COVID-19 pandemic, this ends up promoting the increase of psychological disorders, such as anxiety and depression. This study aimed to evaluate the workload conditions of agents within the UBSs, applying the NASA-TLX method. As a field analysis, a case study was prepared and the NASA-TLX evaluation method was applied in a UBS, in the city of Franca - SP, the workload of the employees of this UBS was compared in the COVID-19 vaccination activities, in that employees apply COVID-19 vaccines to the public, and in the COVID 19 service/queue organization, in which employees explain, talk and answer questions from the population about how to organize the queues for the application of COVID-19 vaccines. It was concluded that the workload is excessive in both tasks, that the physical performance in the vaccination activity was superior to the service required to the public, and that the effort in the service activity was greater than in the vaccination activity. In addition, the level of achievement, or self-performance, scale was identified as the minimum intensity for both tasks, which can be justified because they are practical and routine actions, not requiring much of self- performance.

© 2013 IEEE.Industry 4.0 is a socioeconomic phenomenon that affects all industries, transforming not only products, processes, and services, but also business models, organizational structures, and strategies, placing human beings at the center of this digital transformation. Researchers have already demonstrated the importance of intangible resources in the Industry 4.0 adoption process. Nevertheless, there is still a gap in empirical research on how these factors evolve during the process. Therefore, the main objective of this study is to identify how these factors influence each other across different Industry 4.0 maturity levels. To achieve this goal, a qualitative approach was used with multiple case studies comparing responses from companies at higher Industry 4.0 maturity levels and contrasting them with the responses from companies at lower levels, distilling aggregate dimensions through an inductive coding procedure. Experts evaluated the results to find relations between the aggregate dimensions, their evolution and influence on each other. As a result, a conceptual framework was developed that demonstrates the dynamics of intangible factors that could be used by any company to nurture its own Intellectual Capital as a groundwork for the adoption of Industry 4.0. Among these dynamics, the central role of engaged leaders was highlighted in developing structural capital factors. Future studies should conduct interviews with more companies from other industrial sectors as well as on the implementation and management of Intellectual Capital in manufacturing companies to assess the applicability of the proposed conceptual framework.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.The costs involved in the design, manufacture, certification and maintenance of a helicopter have grown over the past few years. In the certification phase of embedded systems, their safety levels and their performance requirements are verified. The helicopter engine is a system that must be reliable and capable of providing the necessary power to produce lift and controllability for the aircraft. In this work was developed a computer model to evaluate the helicopter engine’s performance under any flight conditions and the pilot’s inputs. The developed software was incorporated as a module in a flight test simulator at the Flight Tests and Research Institute (IPEV) which belongs to the Brazilian Air Force. This simulation tool allows foreseeing and investigating possible situations that may occur during actual flight tests, improving safety and reducing costs. Using MATLAB® Simulink, it was possible to run at the same time: an iterative and a non-iterative methodology, a control system to set the fuel flow schedule, based on several inputs generated from the thermodynamic model. Based on classic thermodynamics laws and differential equations, the particularities due to the helicopter application were adjusted: the influence of the pilot’s commands; performance requirements; running line control; and the fuel flow control system. The simulation results were compared with commercial gas turbine performance simulation software and with the data provided by the IPEV in five real flight tests. These data were also used for obtaining engine output power requirements according to collective stick position.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.The tip clearance is the gap between the rotor blade row and its casing. In this region, a leakage flow on the rotor blade tip is induced by pressure differences from rotor blade pressure side to suction side, resulting in a loss in the turbomachine efficiency and drop in performance. High pressure turbines (HPT) operate in the limit of the energy transfer process with low-aspect ratio blades and high-pressure loading. The tip clearance loss is significant when compared with other loss sources. To minimize the performance drop, different desensitization techniques were tested for turbulent flow in steady state. First, the HPT developed by NASA in the Energy Efficient Engine (E3) program was studied with its original configuration of rotor tip, also called flat-tip. Then, the winglet was implemented on rotor tip geometry, for both suction and pressure sides. Numerical simulations using the computational fluid dynamics were performed, and the results are compared with experimental data for both cases. The results show that in general, for the same HPT pressure ratio, the use of winglet on the rotor tip pressure side achieved the best results showing an increase in efficiency of 1.025 % for 3.7 of pressure ratio. Even the winglet on the rotor tip suction side presented an efficiency increase of 0.625 % for 3.7 of pressure ratio compared with flat-tip rotor configuration. Overall, both winglet configurations obtained results better than the common rotor blade flat-tip geometry, for the same pressure ratio operational condition.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.For a long time, thermal power plants play important roles in world electricity and are expected to continue, at least, in the next decades. However, the finitude of fossil fuel sources leads to the crucial need for improving the existing power generation systems. In this study, an in-house computational code was developed and validated to evaluate the energy, exergy and economic performance for thermal power plants applications. Based on operating data of an actual lignite coal-fired steam power plant, two cycles were designed and compared. In the cycle in which more components were added, the fuel consumption was 9.44% lower to produce the same amount of power, making more effective use of the fuel resource. This substantial reduction in fuel consumption reflected lower electricity average costs for this plant. Comparing to the electricity price of a country using the same type of fuel, it was found that it could be lower by 1.62 percentage points for household consumers. Although the higher costs with capital investment and operational and maintenance (O&M) due to the addition of these components, the attractive economic performance of the cycle reduces the annual fuel costs and offsets the increase in capital and O&M costs.

© 2022 Elsevier Masson SASAxial turbines are machines widely used in different engineering applications. Due to their constructive characteristics, they must have a space between the rotor blades and the turbine casing, called tip clearance. Unfortunately, this gap allows a part of the fluid to leak from the pressure side to the suction side of the rotor blades. This leakage is undesirable and represents an energy loss. A way to avoid part of this loss is through the use of desensitization techniques. Although the use of these techniques is widely known, no studies in the open literature have evaluated these techniques in hydraulic turbines. This work presents a numerical analysis of squealer desensitization techniques applied in a hydraulic axial turbine. The turbomachine under study is the first stage of the hydraulic axial turbine used in the Low Pressure Oxidizer Turbopump (LPOTP) of the Space Shuttle Main Engine (SSME). Numerical simulations were performed using CFX v.19.2 software, and computational meshes were generated in ICEM v.19.2 software. Initially, the computational model was validated, using the experimental results published by the National Aeronautics and Space Administration (NASA). A parametric analysis was performed considering the variation in squealer cavity depth and rim thickness. The study found that the squealer cavity depth has a greater influence on the stage performance than its rim thickness. The tendency is that the greater the cavity depth, the greater the stage efficiency. One of the squealer geometries analyzed allowed an average increased efficiency of 1.43%, over the entire turbine operational range. The results obtained also show that the application of the proposed geometries would enable the reduction in cavitation close to the trailing edge of the rotor blades. This result is extremely valuable, as it can impact the life cycle of the turbine.

© 2021 Elsevier Inc.The present work describes the implementation of an implicit time-integration numerical scheme to solve viscous flows in an in-house CFD solver. The scheme is developed to calculate engineering problems involving compressible flows. This work extends the defect-correction technique for the 3D flow calculations, and all mathematical formulations are described. The CFD solver is based on the finite-volume method (FVM) to calculate the three-dimensional flow and can be applied to solve unstructured meshes. The current implementation uses the Flux-Difference Splitting method (FDS) developed by Roe combined with the MUSCL method and the Venkatakrishnan flux limiters to provide better accuracy of the numerical solutions. The implicit time-integration scheme was linearized applying the backward Euler method on the left-hand side (LHS) and a Newton-type linearization on the right-hand side (RHS) of the governing equations. The Jacobian matrix was computed analytically for the inviscid fluxes using the Roe fluxes, and for the viscous fluxes differentiating the conservative vector. Earlier work by Cavalca et al. (2018) showed the robustness and accuracy of this implicit solver to predict inviscid flows over the airfoil and into the supersonic nozzle. Finally, the Gauss-Seidel (GS) iterative method was applied to solve the resultant sparse and large system of equations. These numerical schemes and methods were applied to solve the laminar flow over a flat plate. Afterwards, the numerical solution was validated and verified with the exact Blasius solution. From the results, the numerical simulations exhibited superior robustness of the implicit-defect correction scheme when compared with the explicit scheme for compressible flows. All numerical particularities and their implementations are detailed in this paper.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.Variable cycle engines promise to enable adaptive cycles that give close to optimal performance over a wide range of conflicting mission requirements, such as low altitude high speed flight and supercruise still providing excellent range. Modelling such engines pose challenges for general purpose software since variable geometry gas paths modify the underlying set of equations being solved. It is possible to use multiple engine models transferring design data between the models. This, however, creates a high risk for inconsistency and modelling error. It is more attractive if the solutions obtained could be determined using the same model. In this work an in-house software was developed to model an Adaptive Cycle Engine (ACE). This development was used to show how variable cycle mode switches can be integrated into general purpose performance tools. The variable cycle engine uses a FLADE, which is a "fan on blade" component, to extend its range and to provide improved subsonic performance. The individual impact of the components, its effect on propulsion performance parameters and in the engine installation were analyzed as the main results. The contribution from this paper is thus two-fold, firstly the paper goes ahead and proposes new methods for the simulation of mode switching in generic performance tools by introducing dynamic equation systems. Secondly, the paper then studies the FLADE component and its potential performance benefits if added to a conventional turbofan architecture.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.An Axial Turbine Blade Tip has a great influence on its flow behavior and performance. Due to the clearance between the turbine casing and the rotor blades tips, part of the flow leaks from the pressure side to the suction side. This leakage reduces the turbomachine efficiency, and therefore must be minimized. Over the years, the use of desensitization techniques has proven to be an excellent strategy for reducing this unwanted flow. These techniques, however, has only been studied in machines that operate with compressible fluids. The objective of this work is to verify the effects of two Winglet geometries in the first stage of the Liquid Oxygen (LOX) Turbine used as booster in the Space Shuttle Main Engine (SSME). The two Winglet geometries evaluated have identical thickness and width, being differentiated by their trailing edge region configuration. In this region, the first geometry (W1) connects to the trailing edge with an angle close to 90°, while the second geometry (W2) presents a smooth connection. The results obtained show that it is possible to improve the stage efficiency depending on the geometry adopted, as well as to analyze the cavitation phenomenon. The mesh generation and simulations were done using a commercial software and the 3D flow calculations were based on the Reynolds Averaged Navier-Stokes (RANS) equations.

Copyright © 2022 by ASME.The gas turbine industry requires extensive knowledge in several areas of engineering, and since both industry and academy continuously develop new approaches, technologies, and models, usually, there is not enough time to cover all the relevant subjects in one or two-semester courses for undergraduate or graduate students. In previous work, the authors have presented an interactive platform for the preliminary design of single-stage axial turbines with uncooled blades, for use at the undergraduate courses offered by the Turbomachine Department at Aeronautics Institute of Technology to accelerate the learning process. The present work aims to present an expansion of this interactive learning platform, with the inclusion of a module for the thermodynamic cycle study, a module for off-design calculations, and the generation of a PDF file containing the step-by-step solution memorial with all the equations and values used in the design. The work also presents a structure for the conduction of a graduate course in turbomachines focused on the design of axial turbines. It comprehends theory and exercise classes, oriented study with the interactive learning platform, and a project in which the students have to implement some of the modules and run test cases. The authors observed more interest of the students and higher quality questions in the classes while using the interactive platform or programming, developing a better understanding of the design process until the end of the course. Also, while, in previous semesters, the preliminary design occupied almost half of the 48-hour course, it took only 12-hour to cover the same subject, granting time to more advanced topics, such as blade cooling, off-design performance and computational fluid dynamics simulations.

Copyright © 2022 by ASME.Passive wall treatments with circumferential grooves in axial compressors proved to be effective in increasing the compressor stall margin in previous researches by creating a resistance to the flow that leaks in the tip clearance region of the compressor, from the rotor blade pressure side to the suction side. 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 rotor row used in a four-stage axial flow compressor. 3D CFD flow simulations were performed in order to evaluate all the specified configurations aiming to find improvements on compressor stall margin. Investigations on the compressor flow characteristics were realized and the stall margin variations were determined. The numerical simulations were performed based on the Reynolds-Averaged Navier Stokes equations and the turbulence model was the k-ω SST. After the simulations, several rotational speeds of the compressor map characteristics, including the design-point rotational speed, were obtained for the case without casing treatment (smooth wall case) and for the case with circumferential grooves. In the results, passive wall treatment with circumferential grooves demonstrated an improvement in the compressor stall margin, especially for N=0.60 and N=0.90 rotational speeds.

© 2022, American Institute of Aeronautics and Astronautics Inc.. All rights reserved.Waste heat recovery is a key pathway to achieving reduced emissions and improved system efficiency. Waste heat can potentially be converted to electric power by several methods. One of the most effective methods is based on using a supercritical CO2 waste heat recovery power system. The sCO2 power system has advantages because of component compactness, which is an important consideration for aircraft integration. The present work focuses on implementing the supercritical CO2 power system into both current and next-generation aircraft engines that may use different fuels, such as hydrogen, ammonia, or sustainable aviation fuel (SAF). The first part of the work is focused on detailed optimization of the sCO2 waste heat system for a real aircraft engine with two sCO2 cycle configurations. The second part of the work is focused on detailed design of the heat exchangers, including weight and pressure drop calculation. The simulation was done using an in-house computer program for gas turbine performance and for the sCO2 cycle. The results show the potential utilization of waste heat in different operational regimes: idling on the ground, cruise, landing, and takeoff. One engine (nominal thrust of 9kN) with two different waste recovery units are investigated. The results demonstrated that the waste heat unit could generate an additional 100-200 kW for the 9-kN-engine (under cruise operation), which may reduce fuel consumption, even if the sCO2 system weight is around 800 lbm / 364 kg.

© 2021 Elsevier LtdThe requirements of Liquid Propellant Rocket Engine (LPRE) are high for thrust, specific impulse, and flow rate; thus, its components also have strict requirements. For the turbopumps (TPs), this means high flow rate, high rotational speed, and high pressure ratio, which makes their operations susceptible to the cavitation phenomenon, as observed in two previous works. In the first, cavitation regions were observed in the first stage of the Space Shuttle Main Engine (SSME) Liquid Oxygen (LOX) booster turbine, for 3.0, 5.5, and 8.0% tip clearances (relative to rotor blade height), using monophase flow (Lindquist Whitacker et al., 2017). In the second, the simulations were performed with multiphase flow, producing results more physically coherent for the 3.0% gap configuration (Whitacker et al., 2018). The characteristics of both types of simulations in space propulsion applications still require better understanding. Therefore, to compare monophase and multiphase results at various operating points and turbine configurations, steady-state turbulent 3-D Computational Fluid Dynamics (CFD) simulations were performed, based on Reynolds-Averaged Navier-Stokes (RANS) formulation. The same three tip configurations for the turbine first stage were simulated, and the calculations were validated using experimental results from the National Aeronautics and Space Administration (NASA) (Boynton and Rohlik, 1976). This made it possible to verify the effect of the tip clearance on the machine performance and internal flowfield. When the gap increased, the pressure loading decreased in a large region of the blade tip, the interaction was greater between the Tip Clearance Vortex (TCV) and a vortex generated around the shroud cavitation region (Cavitation Vortex - CV), and this interaction moved towards the middle of the blade-to-blade passage. Thus, the losses increased and the efficiency decreased. Various comparative aspects between the simulations using both mono and multiphase numerical schemes are also discussed.

© 2022 American Chemical Society. All rights reserved.Traditional osteosarcoma therapies tend to focus solely on eradicating residual cancer cells and often fail to promote local bone regeneration and even inhibit it due to lack of precise control over target cells, i.e., the treatment affects both normal and cancer cells. Typically, multistep procedures are required for optimal efficacy. Here, we found that a silica-based bioactive material containing 3 mol % gallium oxide selectively kills human osteosarcoma cells and presents excellent in vivo osteointegration, while showing no local or systemic toxicity. Cell culture media conditioned with the proposed material was able to kill 41% of osteosarcoma cells, and no significant deleterious effect on normal human osteoblasts was observed. In addition, rats treated with the gallium-doped material showed excellent material-bone integration with no sign of local toxicity or implant rejection. Systemic biocompatibility investigation did not indicate any sign of toxicity, with no presence of fibrosis or cellular infiltrate in the histological microstructure of the liver and kidneys after 56 days of observation. Taken together, these results show that synergistic bone regeneration and targeted cancer therapy can be combined, paving the way toward new bone cancer treatment approaches.

© 2022 Elsevier LtdThe sol-gel method is one of the most used methods due to its outstanding capacity to obtain alkaline-earth phosphosilicate bioactive glass with high bioactivity. This efficient synthesis method involves several stages constituted by intermediate chemical reactions, which are governed by mechanisms and kinetic parameters that lead to the formation of the precursor gel of the vitreous matrix. Although the sol-gel method has been widely used for the preparation of materials, some steps are still not completely understood and that affect the final properties of the synthesized materials. For instance, the hydrolysis reaction of triethyl phosphate (TEP) which, similarly to tetraethyl orthosilicate (TEOS), is assumed to be complete in the stage of formation of the precursor gel of the glass matrix. Furthermore, the SN2-type mechanism for the hydrolysis of TEP is widely assumed. However, the absence of studies that support these presumptions fully justifies the use of theoretical methods to gain information about the hydrolysis of TEP within the sol-gel synthesis of 58S bioactive glass. Density functional theory (DFT) and molecular dynamics (MD) simulations were used to study the reaction mechanisms and kinetic behavior of TEP hydrolysis. Our results show that the TEP hydrolysis reaction is very slow in its three stages, occurring not only via the SN2 mechanism with configuration inversion (SN2–I), as is commonly reported in the literature, but also via SN2 with configuration retention (SN2–R). Furthermore, it was found that the hydrolysis reaction via SN2–I occurs with faster kinetics than SN2–R. This behavior was observed for the three stages of TEP hydrolysis, both in protonated and non-protonated solutions. Based on our findings on the mechanisms and kinetics of triethyl phosphate hydrolysis reactions, a simple chemical model for the formation of calcium pyrophosphate crystalline domains in 58S sol-gel bioactive glass was proposed. In our model, TEOS undergoes rapid hydrolysis, followed by immediate condensation leading to the formation of three-dimensional silica gels, that permeate non-hydrolyzed TEP molecules due to their slow kinetic rate. This mismatch between the reactions of precursor alkoxides in acidic medium, results in a strong tendency in the formation of a glassy microstructure with low structural homogeneity characterized by crystalline domains of calcium pyrophosphate permeated by a silica-rich glass matrix.

© 2021The pioneeristic work of Hench led to the development of a calcium sodium phosphosilicate composition called 45S5 Bioglass®, which has been investigated extensively for applications in the field of bone repair and regeneration because of its bioactivity, i.e., ability to form a bond to living bone. The bioactivity of silicate glass is qualitatively associated with the development over time of the apatite layer on a bioactive glass, while quantitatively it would be related to how fast the formation of this crystalline phase occurs. In this work, (Camoltensaltbath2+|Naglass+) ion exchange in a molten salt bath (MSB) was employed for modifying the glass surface aiming to create a more reactive glass in a thin shell that surrounds the vitreous core, which preserves all the bioactivity characteristics of 45S5 Bioglass® composition. The 45S5@Ca45S5 core-shell-structured bioactive glass is characterized by a vitreous matrix enriched with calcium and a highly depolymerized silicate network. The presence of calcium-rich glass composition restricted to a thin shell acts as a catalyst, accelerating all the earlier events that occur at the glass/solution interface. The kinetics of deposition of the silica-gel and apatite layers was investigated by FTIR and 31P MAS NMR, respectively. The results suggest that the modification of the glass surface causes not only a reduction in the formation time of silica-gel and amorphous calcium phosphate on the glass surface but also induced the formation of the apatite phase with a higher degree of crystallinity.

© 2022 Elsevier Editora Ltda. All rights reserved.A Ti-50.8Ni (at.%)/Ti-55.9Ni (wt.%) VIM processed ingot was rotary swaged and rolled in parallel, obtaining bars with a total Area Reduction above 90% (from forged/rolled raw state one). Throughout the successive stages, the microstructural evolution, thermal and mechanical properties were compared. Deformation bands, grain morphology, precipitates and oxidation were evaluated (by OM and SEM/EDS). An essentially (∼100%) austenitic phase was detected at room temperature (via XRD/Rietveld method), while the Martensitic Transformation temperatures occurred at negative temperatures (via DSC). The rolled bar got through the process more regularly, with homogeneous and refined structure. Typical defects such as superficial microcracks and creases were relevant in the last stages of the two-dies rotary swaging with inductive heating. The work hardening level (via Hardness Test) was similar in both metal forming processes, being 5-7% more pronounced at the edge area of the bars due to redundant work.

© 2022 Elsevier B.V.This paper presents the results of the Density Functional Theory (DFT) calculations and reactive molecular dynamics (RMD) simulations of the furazanotetrazinedioxide (FTDO) explosive, a novel highly energetic material. The details of the mechanism of the FTDO decomposition have been elucidated for the first time. The calculated activation energy was found to be 30.96 ± 2.25 kJ/mol. The DFT calculation results suggested that FTDO is prone to the fragmentation and decomposition processes. The study results present original mechanisms for the FTDO detonation/decomposition along with the values for the activation energy and frequency factor with high linear determination coefficient.

© 2021 Elsevier LtdThe current work presents the simulation of the pyrolysis and combustion of alternative jet fuels by reactive force field molecular dynamics methods. A comparison has been done between saturated hydrocarbon farnesane and two unsaturated compounds, α-farnesene and β-farnesene, all of them obtained by the fermentation of sugars present in sugarcane juice. The pyrolysis and combustion mechanisms were elucidated for all the three species at a specified temperature. Significant differences have been observed among the compound reactions during the decompositions. Using a first-order approach, the Arrhenius parameters of the global process were obtained with three different temperatures, held constant over time. For the pyrolysis, the obtained activation energies for farnesane, α-farnesene, and β-farnesene were 132.55, 117.28, and 112.88 kJ mol−1, respectively, and for the combustion, the obtained activation energies were 71.63, 37.99, and 37.98 kJ mol−1, respectively. These data are compatible with the results found in the literature for hydrocarbon fuels. A detailed computational study of all three compounds was performed using the B3LYP/6–311 + G(d,p) approach in the gas phase. Analysis of structures, NBO charges, FMOs, MEP plots, and global reactivity parameters unequivocally supports the simulation results obtained using the ReaxFF code, proving noticeably higher potential reactivity of α- and β-farnesenes compared to farnesane, and furthermore higher reactivity of β-farnesene compared to α-farnesene.

© 2021 Wiley Periodicals LLC.The solid composite propellant is a viscoelastic material that retains the treatment received during its all-useful life. As a result, its manufacturing conditions induce differences in its final mechanical properties. The present study aims to evaluate the influence of the type and size of the reactor and the effects of the heating interruption during curing on the final mechanical properties of the propellant. Thus, four production processes with identical propellant formulations were performed in four different reactors. One of them was vertical, while the others were horizontal reactors. The heating interruption during curing was performed in 10 samples, at different moments of the curing process and with different duration. The study determines that vertical reactors tend to produce propellants less rigid than those produced in the horizontal type. In addition, the bigger the reactor size, the less rigid the propellant becomes. Finally, the heating interruptions at the beginning of the curing process tend to be insignificant. However, when they occur in an advanced stage of the curing process, they tend to hinder the curing progress, being more significant for interruptions of medium duration.

© 2022, The Author(s).The enormous magnitude of 2 billion tons of alloys produced per year demands a change in design philosophy to make materials environmentally, economically, and socially more sustainable. This disqualifies the use of critical elements that are rare or have questionable origin. Amongst the major alloy strengthening mechanisms, a high-dispersion of second-phase precipitates with sizes in the nanometre range is particularly effective for achieving ultra-high strength. Here, we propose an alternative segregation-based strategy for sustainable steels, free of critical elements, which are rendered ultrastrong by second-phase nano-precipitation. We increase the Mn-content in a supersaturated, metastable Fe-Mn solid solution to trigger compositional fluctuations and nano-segregation in the bulk. These fluctuations act as precursors for the nucleation of an unexpected α-Mn phase, which impedes dislocation motion, thus enabling precipitation strengthening. Our steel outperforms most common commercial alloys, yet it is free of critical elements, making it a new platform for sustainable alloy design.

© 2022, ASM International.Additive manufacturing (AM) has emerged as an outstanding technique for obtaining complex geometries and custom parts, without the material loss of conventional subtractive manufacturing processes. In this work, AISI 316L stainless steel specimens were fabricated by laser powder bed fusion (L-PBF), and its microstructure was characterized by several techniques. Tensile tests with in situ x-ray diffraction (XRD) measurements were performed using synchrotron radiation. Stress–strain curves and diffractograms were obtained for the as-printed AM 316L, annealed AM 316L and conventional/rolled 316L samples for comparison. The results indicated lower ductility for the AM samples when compared to the sheet. This can be a result of the remaining porosity associated with the AM process. The annealing of the AM samples led to a reduction of the residual stress and an improvement of ductility without significant loss on the ultimate tensile strength. In situ XRD data indicated that AM samples did not undergo phase transformation during straining, maintaining a fully austenitic microstructure and preventing a transformation-induced plasticity (TRIP) effect. On the other hand, in the rolled sample, peaks of α′-martensite were identified. Electron backscattered diffraction (EBSD) measurements indicated that a random texture was achieved by the parameters and scanning strategy used. The results indicate that process parameters must be carefully chosen in order to avoid porosity, and excessive residual stresses, features that directly affect the mechanical behavior of the material.

© 2022 Universidade Federal de Sao Carlos. All rights reserved.The effect of temperature was investigated on the consolidation of blended elemental powders of aluminum and copper by equal channel angular pressing (ECAP). Aluminum and Copper powders (1:1% vol.) were blended and consolidated in a 90° ECAP die at room (RT) and cryogenic temperatures (CT - ∼77 K). ECAP samples were pressed until 4 passes at room temperature in route Bc. As a reference, a sample was obtained by conventional uniaxial pressing. The obtained results indicated a much denser (>99.5%) and harder structure by cryogenic ECAP. The hardness after one pass at CT was comparable with 4 passes at room temperature. Tensile tests performed at CT for materials with similar chemical composition showed a simultaneous increase in strength and ductility at CT, corroborating the results obtained by ECAP. The partial suppression of dynamic recovery and the activation and the transition between deformation mechanisms at CT, as well as stacking fault energies (SFE) of such metals, played an important role in these results. Copper presented a much higher capability of strain hardening than aluminum, due to its lower SFE and much lower homologous temperature. X-ray diffraction indicated a strong correlation between the variation of average microstrain and the variation of hardness on both metals. The results of this study demonstrated the great potential of the application of very low temperatures for the obtaining of deformation metal-metal composites.

© This work deals with the elastostatic identification of industrial manipulators. By reviewing the basics of the physical elastic properties of both links and joints in the framework of the lumped stiffness modeling techniques, the Gramian nature of the stiffness matrices has been found out adequate to do so. Then, a novel optimization method has been developed, which incorporates the Gramian matrix formulation along a non-linear optimization process, acting as an intrinsic constraint for the conservativeness of the elastostatic modeling. Numerical and experimental analyses evince the effectiveness of the proposed method, as the elastostatic models obtained by means of the proposed technique predict more than 93.7% of the compliance deviations of a real industrial robot. The proposed method is simple enough to be jointly applicable to the most recent elastostatic model reduction techniques.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.Riveting processes are widely used in aeronautical structures, mainly in thin shell structures, like wing and fuselage panels. During such processes, the product shape is slightly changed. That slight geometrical change can be detected by measurement systems or even visually in some cases. The riveting-induced shape alterations, may affect, in some amount, the aerodynamics and the manufacturing cycle and cost of the final product. One cause of the deformations, among many others, is the cumulative effect of the diametral expansions, along the riveting lines. Aerodynamic surfaces, under such phenomenon, may be sensibly affected. The consequences are not deeply addressed in the current literature. The shape problem is not considered in the design of the riveting systems either, and the problem may be intensified by automatic or robotized riveting systems once those are set to accomplish an optimized cycle time, but no consideration is given regarding to the minimization of the possible shape distortion. Such effect may become a limitation when developing manufacturing systems for high performance wings in the aeronautical industry. In this work, one selected typical 2D airfoil section is assessed for shape deviations at the relative proportions normally induced by riveting processes. Due to the problem complexity and to simplify this assessment, the simulations herein are limited to 2D flow (no 3D effects addressed). The modified airfoils are numerically evaluated in a 2D flow software code, using the panels’ method, and the results are compared with the original airfoil coefficients (Cl, Cd, Cl/Cd). The objective of this work is to understand the overall effects produced by the shape deviations, their main contributors and the relevance to the conception of new automatic riveting systems aiming wing structural assemblies.

© 2021 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The riveting process is widely used by the aeronautical industry, mainly in joining sheet metal aluminum alloys. In this process, squeezing force is one of the main setup parameters used to control the quality of the joining process, mainly on automated riveting machines. That squeezing force can be estimated or checked based on the rivet material parameters (hardening constants) and on the driven rivet head dimensions before and after the force application. The equation, commonly used in literature, tends to underestimate, by a relatively small amount, the squeezing force at high squeezing ratios and slightly overestimate at median ratios. This is due to the influence of the following two factors not considered in the original equation: Riveted grip thickness and friction among rivet, sheet, and punch tools. In this work, a revised algebraic model is proposed. The new model is still simple and easily adaptable to a spreadsheet or to a computer code like MATLAB®, R®, Scilab®, or Python®. Using the proposed model, the calculated squeeze force values tend to be more accurate at the squeeze ratios normally used by the aeronautical industry.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.This work extends the classic lunar patched-conic approximation model for Earth–Moon transfers by adding two complexities: the eccentricity of the Moon’s orbit around Earth and the eccentricity of the terminal orbits. In this way, the initial low Earth orbit (LEO) and the final low Moon orbit (LMO) are assumed elliptic. The transfer trajectory is performed by application of two impulses at the terminal orbits; however, they are not necessarily applied at the pericenter of the terminal orbits (LEO and LMO). The positions of application of the impulses are specified by the values of the true anomalies that define the point of departure in the LEO and the point of arrival in the LMO. The transfer problem is also formulated in the context of the planar elliptic restricted three-body problem with the same complexities: eccentricity of the primaries Earth and Moon, and the eccentricity of the terminal orbits. However, an additional final constraint is added relating the flight path angle of the transfer trajectory and the one of the LMO at the arrival time. In the proposed patched-conic approximation, this constraint does not appear as it is solved geometrically. In both models, a two-point boundary value problem solves the Earth–Moon trajectory. A one-degree-of-freedom problem, which uses the Moon’s position as a parameters, and a two-degree-of- freedom optimization problem, which sets the Moon’s position as an unknown to be solved, are also formulated in both models and solved by the sequential-gradient restoration algorithm. The results show some impossible configurations of arrival at LMO, as well as the agreements between the models. Also, a huge importance in the orientation of the LEO, determined by its argument of pericenter, is observed in the fuel consumption. So, a study of penalty on the fuel consumption due to the use of non-optimal values of argument of pericenter of the LEO is performed.

Copyright © (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.There are some approaches for updating models to later model the aeroelastic behavior, and in this work, the Modal Assurance Criterion (MAC) helps identify the parameters. The objective of this work was to update the finite element model for the EOLO aircraft. We used the modal shapes derived from Ground Test Vibration (GVT) as a basis of comparison for the MAC, in addition to using the Nastran software to optimize the stiffness properties of the analytical model of the EOLO aircraft. It noted that the natural frequencies of the updated model approached the GVT data and the cross-correlation improved, but the correlation was far from ideal. Therefore, the model was updated and improved over the initial model.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.This paper presents the identification of an Unmanned Aerial System (UAS) with flexible wings from open-loop data using subspace methods. For aerodynamic and flight control systems, a reliable model is important to comprehend the system behaviour and to design a feedback loop, that can be applied as well to minimize the effects of structural flexibility. So, a parametric model identification for flexible aircraft applying subspace techniques was performed. Preliminary results presented in this paper are related to identification using synthetic data. Finally, it is shown the experimental results from the first flight test performed in open-loop operation. The experimental results reveals that subspace methods estimate a state-space model suitable, with better fit for the range of frequencies of the experimental data. Therefore, it was not possible to obtain a representative model for a broader frequency range, however, this is not a limitation of the method, but a persistent excitation problem associated with the limited frequencies in the input signal.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.Synthetic Air Data Systems are airspeed estimation algorithms. Such algorithms are built using measurements from sensors other than the classical Pitot tubes, from which airspeed estimates can be computed. This paper presents brief discussions over three direct estimation algorithms that use inertial sensors (IRS) and GPS as sources of information. It is also proposed and tested a recursive airspeed and thrust estimation (RATE) algorithm. Finally, a simple implementation using Extended Kalman Filter (EKF) is tested and results are compared. The possibility to use angle-of-attack and/or temperature probes is also discussed. We also discuss practical aspects regarding airspeed, altitude and temperature estimations.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.Subscale aircraft have been used for decades to design new aircraft and evaluate new design techniques. The acquisition of in-flight data from subscale aircraft is already possible today, such as a manned or fullscale aircraft. Thus, more reliable flight simulators are built for flight quality analysis and control design. This work aims to implement a data acquisition and processing system, with the objective of identifying the complete dynamics of a subscale aircraft, model Cessna 182.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The development of microelectronics combined with the cheapness of manufacturing processes has allowed the construction of subscale models equipped with sensors and control systems equivalent to a real aircraft. This work analyses the Generic Future Fighter (GFF) subscale concept developed by Linköping University under the Future Aircraft Design and Demonstration (FADEMO) project. The GFF subscale is a radio-controlled aircraft with 14% of the size of the full-scale concept aircraft. A Stability Augmentation System (SAS) will be designed to stabilize the longitudinal dynamics for different positions of the c.g., artificially modified for three different positions. Despite the several control techniques currently available, methods such as the Linear Quadratic Regulator (LQR) are still adopted for the stability control of aircraft in flight. However the LQR method present in their classic form, limitations to incorporate performance parameters and operational restrictions in the design phase. A promising alternative to circumvent this problem is the use of Linear Matrix Inequalities (LMIs) as a tool to convert stability and control problems into optimization problems. This work presented an LQR-LMI formulation augmented by D-stability criterion to simplify the determination of a single feedback gain matrix that guarantees the stability and keeps the flight characteristics by varying the c.g. position.

© 2022In this paper, optimal solutions are investigated for a transfer from a parking orbit around the Moon to a halo orbit around L2 of the Earth-Moon system. The transfers are executed by applying a single maneuver and exploiting the stable invariant manifold of the hyperbolic parking solution at arrival. In this regard, an optimization problem is proposed where both the orbital characteristics of a parking solution around the Moon (its Keplerian elements) and the characteristics of a transfer trajectory (guided by the stable manifold of the arrival Halo orbit) are considered as variables. The problem involved in the single maneuver transfer is solved using a nonlinear programming method (NLP), which aims to minimize the cost of ΔV within the framework of the Earth-Moon system using the circular restricted three-body problem. The feasibility of this kind of transfer for a Cubesat is shown in this paper through results with low ΔV combined with suitable times of flight.

© 2022 Elsevier LtdThe use of air as heat transfer fluid and a packed bed of rocks as storage medium for a thermal energy system (TES) can be a cost-effective alternative for thermal applications. Here, a porous media turbulent flow (standard k-ε) and heat transfer (local thermal non-equilibrium) model is used to simulate the discharge cycle of such system. Temperature fields of corresponding charging cycles are used as initial conditions. Effects of varying mass flow rates (Re number), porosity, permeability (Da number), thermal conductivity ratio and thermal capacity ratio on the effectiveness of the discharge are compared. The examination of these effects indicated that increasing the mass flow rate improved the effectiveness of the discharge, which was not seen for the charging cycle. Also, increasing porosity improved discharge efficiency more significantly than it did in the charging cycle. In both charge and discharge cycles the effect of permeability is significant and reducing Da number improved temperature stratification and efficiencies. The effect of the thermal conductivity ratio was mostly seen on the outlet temperatures, where lower ratios allowed for higher temperature values. Increasing the thermal capacity ratio improved charging effectiveness but, on the discharge cycle, cycle this effect was reduced. Moreover, for lower Re number flows, increasing this ratio reduced efficiency indicating that the mass flow rate should be matched carefully with the thermal capacity of the system. All these effects have important implications which should be taken into consideration when designing an effective thermal energy storage system.

© 2022 Elsevier LtdIn this work, the process of filtration of particles carried out by turbulent flows is investigated. The applied mathematical framework considers turbulent flow regime in the clear region and within the filter. The motivation for this work is to get insight on possible use of filters to separate thermite mixtures from a carrier phase and their use in thermal plug and abandonment of oil wells. Axisymmetric simulations are performed using the finite volume method. A macroscopic k-ε model is applied to handle turbulence. Pressure drop, stream function and turbulence field are computed. Using correlations in the literature, filter efficiencies are estimated based on calculated flow and pressure fields. Reynolds numbers varied from 2.3 × 103 to 4.6 × 104 for different permeabilities K ranging from 3.47 × 10−9 m2 to 8.89 × 10−9 m2, corresponding to filter particle diameters dp = 1.0 × 10−2 m and 1.0 × 10−3 m and different porosities (0.5 to 0.8). The results showed that pressure drop is strongly affected by porosity, permeability and Reynolds number; the stream function maps indicated wider stagnant zones for filters with larger particle diameters (higher permeabilities); turbulence fields showed slight generation of turbulence inside the filtration zone. The results for efficiency illustrated that, in case of filtrating thermite, higher inlet velocities, filters with particles of size 1.0 × 10−3 m and lower porosity filters favor the collection mechanism.

© 2022 by the author. Licensee MDPI, Basel, Switzerland.In this article, a concept named double decomposition, which is used to model turbulent flows in porous media, is examined. This concept is based on the idea that in a turbulent flow through a porous matrix, local instantaneous variables can be averaged in time and space, simultaneously. Depending on how these operators are applied, averaged equations take different forms. In this article, instantaneous local equations are averaged using both operators and a different set of equations resulting from such operations are commented upon. Additional terms proposed for the averaged equations are discussed.

© 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Thermites are powerful energetic materials able to release large amounts of energy in a self-propagating reaction. They have been widely applied in rail welding, pyrotechnics, and material synthesis, as they are highly exothermic. In recent years, there has been an increased interest on applying a thermite reaction in the plug and abandonment of wells due to the possibility of reducing the high cost of this process. However, some primary studies are required to understand these energetic materials and to select the most efficient thermite mixtures to be applied in a plug and abandonment scenario. Although they do not react as simple condensed-phase reactions because of all the complex physicochemical mechanisms involved, they can be characterized and understood by simple principles of thermodynamics. As so, this research presents the importance of the Gibbs free energy concept to determine the candidates of a thermite reaction, in addition to showing how important characteristics of these reactions such as adiabatic temperature and heat released can be calculated using thermodynamic principles. Lastly, the minimization of Gibbs free energy method for determining the final products of a reaction, considering chemical equilibrium, is presented and applied to predict the final products, as a function of temperature, for some of the most powerful thermite mixtures. The conclusion is that, although the 2Al–Fe2O3 thermite reaction has the lower mass and volumetric heat of combustion in comparison with the 2Al–3CuO and 3Be–Fe2O3 thermites, it can reach the highest adiabatic temperature observed due to the lower gaseous mass fraction in the products, which means fewer heat losses due to phase changes. So, the thermite mixture 2Al–Fe2O3 is a promising candidate for the plug and abandonment of mature oil wells.

© 2022In this work was analyzed the fatigue resistance performance of several universal cardan joint for direction column in automotive application. For this purpose, were performed a simulation by finite element (FEA), laboratory fatigue tests and Weibull distribution reliability analyses to evaluate the fatigue life performance of universal joints in according with MAN PV 2892 BR criteria. These analyses were made taking into account a torsional working load in addition to torque applied in the fasten clamp yoke region with the shaft. Additionally, mechanical stakes tests retention was performed in order to attend the requirements of MAN PV 2892 BR. The results indicate that although laboratory fatigue testing exceeds 500,000 cycles, there is an 8% probability that failure will occur at less than the required number of cycles. Thus, the material design and manufacturing process employed, mainly in relation about the amount and mechanical stakes locations and fork roughness, as well as the microstructure inclusions content could bring significant gains in fatigue life in this automotive component.

© 2021, The Author(s), under exclusive licence to Springer Nature B.V.Maraging steels are ultra-high mechanical strength steels based on Ni-Co-Mo-Ti with extra low carbon content (< 0.03%). This steel family belongs to a strategic group of materials with multiple applications, including pressure vessels, aeronautic and aerospace components, and sportive equipment. Thus, the knowledge of stress strain curves behavior performed at slow strain rate tensile tests (SSRT) is very interesting for processing, manufacturing and service from these high-performance alloys. In this work, SSRT tests were performed in maraging 300 and 350 steels in solution treatment and aged conditions (783 K for 6 h). Additionally, the hydrogen embrittlement was evaluated in SSRT performed by cathodic potential applied at −1.2 VSCE in 3.5% NaCl solution. Therefore, an analysis by environmental test was performed by obtention of stress and ductility comparative parameters. The hydrogen diffusion in alpha iron was studied using an electrochemical permeation transfer function. Similarly, a study was performed with Hollomon and Voce constitutive models to describe the strain-hardening behavior of these alloys. There is a lack of information in the literature, the use of these models is very interesting to these alloys in order to describe the mechanical behavior of maraging steels. In this work the experimental values were fitted using an iterative regression method of R2, which provided values close to the unit. The fitting by Voce model provided more accurate predictions at large strain-hardening behavior when compared with Hollomon’s model. The constants values obtained from Voce’s model were evaluated in all treatment conditions establishing a correlation with changes in work hardening. Voce is distinguished from Hollomon in that it allows more precise adjustments of the constants, and this allows a better description of the experimental values obtained from aging and environmental analysis. Finally, the work concludes by presenting an analysis of the behavior of the coefficients under different test conditions studied and correlates the values obtained with the fractographic analysis, demonstrating the models can be used with good accuracy to describe the plastic deformation response of high strength values on maraging 300 and 350 steels.

© 2021, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.18% Ni-Co-Mo-Ti ferrous base alloys are special materials, widely used in the industry of isotopic enrichment after specific annealing and aging thermal treatment. The desirable high mechanical properties can then be attained by adequate aging heat treatment, answering the structural materials specifications required by defense applications in aerospace and nuclear engineering. For instance, the isotopic enrichment, in rocket engine envelope application, when associated with high temperature and chemical residues like acidic solutions, can induce corrosion and hydrogen embrittlement in martensitic microstructure. In order to limit these corrosion and hydrogen embrittlement phenomena, adherent and protective layers of iron oxides can be grown on the material’s surface by performing aging treatment in an adequate atmosphere. Due to its application in strategic areas, the characterization of these oxide layers in maraging steels is of importance as well as the understanding of their growth kinetics. For this purpose, several techniques, such as optical microscopy (OM), scanning electron microscopy (SEM), glow discharge optical emission spectroscopy (GDOES), microabrasive wear testing, hardness, grazing incidence X-ray diffraction (GIXRD), and X-ray photoelectron spectroscopy (XPS), have been performed for chemical and structural characterization of the oxide films formed after vapor exposed thermal aging at 510℃. The oxide layer consists of two sub-layers composed by magnetite (Fe3O4) and an external layer of hematite (Fe2O3). A thick interface between the oxide layer and the bulk is enriched in Ti and Mo, whereas the analyses of deep bulk material show an enriched area with Ni and Co.

© 2022Recent advances applying the vibration correlation technique as a nondestructive experimental procedure for determining the in-situ buckling load of unstiffened and skin-dominated stiffened cylindrical shells are showing promising results. Previous studies associated the applicability and the convergence of the mentioned technique with the knockdown factor to be estimated. It is upon this basis that this paper proposes to exploit further this aspect towards a load factor for enhancing the buckling load estimations. The study considers existing validated finite element models for a systematic evaluation of the compliance of the vibration correlation technique and, based on such numerical results, it proposes a load factor for enhanced buckling load estimations. The concept is firstly verified for the numerical results, supporting its establishment. Subsequently, existing experimental results are reevaluated for an assessment of the devised load factor into the buckling load predictions. The appropriate magnitude of the load factors is determined through an iterative study grounded on numerical models that could be defined beforehand. Throughout the numerical- and experimental-based studies, the potential of the proposed load factor is demonstrated towards enhanced VCT buckling load estimations for unstiffened composite cylindrical shells.

© 2022 Elsevier LtdAdhesive bonding technologies are widely used for the assembly of stiffened panels manufactured in advanced composites for structural applications in aeronautics. However, stiffened panels are prone to the occurrence of defects or damage in the skin/stiffener junction, which will reduce the damage tolerance properties and affect structural integrity. The presence of unstable irregularities in the bonding region contributes to the decrease in the level of adhesion, limiting the resistance of the adhesive/laminate interface when subjected to mechanical loads. This article presents an experimental fracture analysis of flat panels with a longitudinal T-stiffener integrated into the skin by secondary bonding. The panels were produced in quasi-isotropic carbon/epoxy laminates with an artificial insert film replacing the adhesive film in the center of the bonding, to induce the initial damage. The tests were performed under cyclic loading followed by static axial compression loading at room temperature up to collapse. The panel selected for visual and fractographic analysis reached buckling instability with 14% of the final load, in the time interval when the failure propagation induced slight reductions in stiffness. The results obtained from this work showed the influence of the failure mechanisms combined with the formation of the failure modes and fractographic aspects that characterized the complexity of the fracture morphology provided by debonding of the skin/stiffener junction. The information revealed was relevant to the understanding of the failure process resulting from a critical defect on secondary bonding joints, applied in the integration of composite stiffened panels for aeronautics applications.

© 2021 Elsevier LtdA semi-analytical model for buckling analysis of stiffened composite panel with debonding defect, subjected to in-plane shear load is developed and verified. The model formulation is based on the Rayleigh–Ritz method combined with the principle of total stationary potential energy. The domain is discretized ensuring the continuity C1, each domain displacement was approximated using a base of polynomial hierarchical functions. Finite element analyses and experimental tests were also performed to verify the proposed model and investigate the influence of the defect size on the panel stability. The proposed semi-analytical model is an efficient and accurate design tool that can be used in the prediction and identification of critical design scenarios for damage tolerant aerostructures.

© The Author(s) 2021.In this article, the structural behavior of co-cured composite joint (CC), co-bonded composite joint (CB), and secondary-bonded composite joint (SB) under Mode II fatigue loading was evaluated. Fatigue performance was evaluated in sub-critical strain energy release rate (SERR) associated with Mode II fatigue induced delamination growth onset. Fatigue tests were carried out using the three-point bending End Notched Flexure test setup for different energy ratios. The experimental results are presented in terms of SERR versus number of cycles, and the SERR threshold for no growth is determined (Gth). Fractographic analyses were performed in order to identify the main failure mechanisms related to each joining technology under Mode II. The results indicated an initial cohesive failure followed by an adhesive failure promoted by crack propagation at the interface between the adhesive and the composite adherend on SB and CB samples, through the coalescence of microcracks that promote the adhesive failure process, leading to fiber pull-out from the matrix and cusps formation in the fracture surface. These results explain the low performance behavior observed on SB and CB bonded techniques. It is worth mentioning that the results and behavior observed in this work are valid only for the laminates, adhesives, surface treatment, and environmental conditions tested herein.

© 2022 Elsevier LtdEfficient yet reliable predictive modelling tools for damage tolerance analysis became an aerospace industry requirement as composite materials provided the potential for design performance. As damage can be separated into interlaminar and intralaminar, different approaches were developed over the years. For fracture analysis of intralaminar damage, a physical link to the Linear Elastic Fracture Mechanics (LEFM) provides a reliable framework for Continuum Damage Mechanics (CDM) models. These models, however, may exhibit pathological problems related to mesh dependence, objectivity and convergence issues. Differently from Cohesive Zone Modelling (CZM) for interlaminar damage, most intralaminar models are based on phenomenological approaches for fatigue analysis and life prediction. This work provides a description of some of the current intralaminar CDM models shortcomings, related to large strain analysis and finite element topology. A novel progressive damage model is proposed where damage variables are linked to the deformation gradient. Additionally, a fatigue damage behaviour under the assumption of a Paris law for crack evolution is implemented in the proposed methodology. Both static and fatigue analysis were performed on a Compact Tension (CT) specimen geometry and compared to experimental data available on the scientific literature. Model predictions and experimental data were confronted allowing for conclusions to be drawn.

© 2022 Elsevier LtdIn recent years a considerable effort has been dedicated to the development of analysis tools that enable the design of damage tolerant structures, particularly in aerospace applications where weight reduction is a crucial requirement. One of these tools developed in recent years is the peridynamic theory, employed to solve numerically complex elastodynamics problems. One of its advantages reported in the literature is the natural ability to simulate the initiation and crack growth without the need for additional numerical procedures commonly employed in other numerical approaches, like in the conventional finite element formulation. Within this context, this paper presents a novel elastoplastic fatigue-induced damage model whose formulation is based on a strain energy framework combined with a smeared crack approach to simulate the damage process without the need of knowing the location of the crack tip and its length within the domain. The proposed model also can predict the mixed-mode damage propagation in ductile materials without knowing a priori the mixity mode ratio. This approach incorporates an analytical methodology based on the material properties that correlate the strain energy calculated away from the crack tip to the expected propagation rate predicted by the Paris Law. The accuracy of the proposed model is verified by comparing the results obtained using an in-house peridynamic FORTRAN code with the experimental results available in the open literature. Some improvements for the peridynamic material parameters are also presented in this paper, which is also verified by using the in-house code.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.Solid propellants are usually characterized by their ballistic and mechanical properties. However, these properties are seldom homogeneous. Processing factors such as multi-batch, casting, curing and post-curing dynamics induce transfer of loads and defects along the propellant. This propellant heterogeneity is responsible for different ballistic and mechanical properties in the grain. This paper presents a novel experimental procedure to characterize the elastic properties of single- and multi-batch solid propellants based on the use of the two-dimensional digital image correlation (DIC) method. The proposed experimental procedure has been applied to two different specimen configurations namely SBIP (single-batch inert propellant) and MBIP (multi-batch inert propellant) propellants. The SBIP specimen was manufactured in a single shot aiming at a more homogeneous mechanical behavior and uniform degree of cure along the propellant length. On the other hand, the MBIP specimen was manufactured in three different stages where each stage has a different degree of cure. Both specimens have a diameter-to-length (L/D) ratio equals to 19, which is an aspect ratio representative of typical large-scale solid-fuel grain rocket configurations. Additionally, in order to validate the in-situ measured properties, tests at small coupon level were also carried out using small cylindrical coupons taken from the same regions of interest used to measure the mechanical properties of the SBIP and MBIP specimens. A very good agreement between the measured local and global (in-situ) strain fields and mechanical properties was found in both testing scales, thus validating the proposed testing procedure based on the DIC technique. Results showed an increase in the elasticity modulus in the specimen bottom due to gravity effects.

© 2022 Elsevier LtdAdhesive bonding technologies are widely used for the assembly of stiffened panels manufactured in advanced composites for structural applications in aeronautics. However, stiffened panels are prone to the occurrence of defects or damage in the skin/stiffener junction, which will reduce the damage tolerance properties and affect structural integrity. The presence of unstable irregularities in the bonding region contributes to the decrease in the level of adhesion, limiting the resistance of the adhesive/laminate interface when subjected to mechanical loads. This article presents an experimental fracture analysis of flat panels with a longitudinal T-stiffener integrated into the skin by secondary bonding. The panels were produced in quasi-isotropic carbon/epoxy laminates with an artificial insert film replacing the adhesive film in the center of the bonding, to induce the initial damage. The tests were performed under cyclic loading followed by static axial compression loading at room temperature up to collapse. The panel selected for visual and fractographic analysis reached buckling instability with 14% of the final load, in the time interval when the failure propagation induced slight reductions in stiffness. The results obtained from this work showed the influence of the failure mechanisms combined with the formation of the failure modes and fractographic aspects that characterized the complexity of the fracture morphology provided by debonding of the skin/stiffener junction. The information revealed was relevant to the understanding of the failure process resulting from a critical defect on secondary bonding joints, applied in the integration of composite stiffened panels for aeronautics applications.

© 2022 Elsevier B.V.The vertically aligned multi-walled carbon nanotubes (VACNTs) / polydimethylsiloxane (PDMS) nanocomposite-based strain sensors presented in this study show different behavior depending on catalyst concentrations for VACNT growth. Under static tensile load, the sensor with lower catalyst concentration shows a high gauge factor (GF~1400), whereupon tunneling effect is the mechanism that dictates the sensitivity. For higher concentrations, the GF decreases (GF~40) and shows an ohmic conduction. Morphological examinations showed VACNTs are homogeneously and randomly distributed as clusters with CNT bridging in the PDMS polymer matrix. Based on dielectric impedance (DI) and direct current (DC) electrical analysis, it was possible to identify that cut-off frequency (fc) increases with VACNTs concentration. Cut-off frequency can also define high sensitivity VACNT sensors with lower VACNT density. When compared with dispersed MWCNT sensors, VACNTs have a reduced fc due to the larger internal resistance variation associated with the high tunneling effect. This effect associated with the high sensitivity of the VACNT/PDMs sensors makes it a key factor to understand the mechanisms responsible for increasing the sensitivity and manufacturing of high GF nanocomposite stretchable sensors.

© 2022 Elsevier LtdThis work describes the impact behaviour of a hybrid fibre-particulate composite composed of glass-carbon fibres and easily dispersible microparticles. The effects of fibre stacking sequence (carbon-C5, glass-G5, C2G3, G3C2, GCGCG and CG3C), particle type (silica, cement and carbon microfibers-CMF) and matrix-fibre volume fraction (40/60 and 60/40) are analysed based on a full factorial design (2 ¹4 ¹6 ¹). A drop-tower impact test characterises the hybrid composites. Fractured surfaces are examined by optical and scanning electron microscopy. The results reveal a significant synergistic effect, in which hybrid composites achieve an overall performance improvement of approximately 20% compared to glass and carbon composites. There is a greater dependence on the inclusion of particles to impact energy and resistance, reaching increased values, especially when silica particles are added. A greater amount of matrix phase ratio leads to a more efficient rheology in terms of fibre-particle interface. In addition, symmetrically placed carbon fibre layers on both sides of the beam under tensile and compressive loads (CG3C) enhance their impact performance in hybrid configuration.

© 2022 Elsevier LtdPeridynamic Theory based models allow simulating the initiation and growth of cracks in solid materials, without the aid of additional methods commonly employed in the conventional finite element formulation. Within this context, a new elastoplastic damage model is proposed to use with the Peridynamic Theory. This proposed damage model combines Von Mises plasticity-based theory with a smeared cracking approach enabling damage prediction within an energy-based framework. The formulation incorporates a mixed-mode propagation criterion to account for the effect of both axial and shear stresses in the simulation, which in turn allows prediction of damage progression in ductile materials under multiaxial loading without knowing a priori the mode mixity ratio. This proposed damage modeling approach can be used within any constitutive peridynamic model, by relying on the displacement field obtained in the simulation.

© 2022 Elsevier LtdThis paper reports the formulation of an aerothermoelastic tool developed to investigate the behavior of flexible beam-like wings made of a hybrid adaptive material. Here, hybrid materials are defined as laminated composites additionally reinforced with embedded shape memory alloy wires. As main novelties, the proposed model couples geometrical, material, and aerodynamic nonlinearities to the thermal dynamics of SMA wires undergoing Joule's effects, thereby establishing a multi-physical nonlinear problem. Geometrical nonlinearities were taken into account via an FE model of a 2D Timoshenko's beam experiencing large deformations. Material nonlinearities were incorporated by a semi-empirical micro-mechanical model that computes the properties of hybrid laminates. To complement, nonlinear aerodynamic effects were introduced via an unsteady strip theory method in the time-domain, along with a nonlinear stall model and an assumption of follower aerodynamic forces. A set of numerical aerothermoelastic cases was performed by assuming various layups and SMA temperatures, with the objective of tailoring the aeroelastic response of hybrid wings. These cases were shown to lead to a considerable reduction in both post-flutter oscillations and post-divergence amplitudes as the SMA temperature increases. The outcomes have indicated compelling evidences on the applicability of embedded SMAs for structural, shape or aeroelastic control of flexible wings.

© 2021 Elsevier LtdA semi-analytical model for buckling analysis of stiffened composite panel with debonding defect, subjected to in-plane shear load is developed and verified. The model formulation is based on the Rayleigh–Ritz method combined with the principle of total stationary potential energy. The domain is discretized ensuring the continuity C1, each domain displacement was approximated using a base of polynomial hierarchical functions. Finite element analyses and experimental tests were also performed to verify the proposed model and investigate the influence of the defect size on the panel stability. The proposed semi-analytical model is an efficient and accurate design tool that can be used in the prediction and identification of critical design scenarios for damage tolerant aerostructures.

© Proceedings of the International Forum of Aeroelasticity and Structural Dynamics 2022, IFASD 2022.This study performs an experimental and numerical investigation on the nonlinear aeroelastic response of composite flat plate-like wings with a ballast at their free tips. The effects of different chord-wise ballast positions are experimentally examined in a set of six rectangular wings laminated with different layups. The proposed numerical model brings forward a nonlinear FE beam model accounting for aerodynamic and geometrical nonlinearities. The latter were taken into account by a total Lagrangian formulation in order to describe the exact kinematics of a Timoshenko’s beam. Nonlinear aerodynamic loads were computed via an unsteady strip theory model in the time-domain, with the Jones approximation for the Wagner’s function. Additionally, a quasi-steady stall model based on an experimental quasi-static stall curve for flat plates was used to interpolate the lift-curve slope. Different nonlinear post-flutter LCO behaviors were obtained for the different ballast positions and layups tested. To conclude, the reasonable correlation between model and experiments indicated that the nonlinear approach performed here was capable to predict the aeroelastic behavior of the tested wings.

© 2022, AIAA International. All rights reserved.The effect of addition of viscoelastic plies on the acoustic scattering quadrupoles near the trailing edge of laminated plates is evaluated. A numerical method is applied to compute the acoustic field scattered by finite flexible plates. For a two-dimensional problem whereby a cantilevered plate scatters sound from a point quadrupole near the free edge, results show that adding viscoelastic layers to a composite plate can modify the far-field sound. Parametric investigations show that this treatment reduces scattered noise near resonance frequencies. Discussions on the positioning and thickness of the viscoelastic layers and operating temperature are provided. The use of outer viscoelastic layers in composite plates is predicted to significantly reduce acoustic scattering near resonances due to structural damping.

© The Author(s) 2021.In this article, the structural behavior of co-cured composite joint (CC), co-bonded composite joint (CB), and secondary-bonded composite joint (SB) under Mode II fatigue loading was evaluated. Fatigue performance was evaluated in sub-critical strain energy release rate (SERR) associated with Mode II fatigue induced delamination growth onset. Fatigue tests were carried out using the three-point bending End Notched Flexure test setup for different energy ratios. The experimental results are presented in terms of SERR versus number of cycles, and the SERR threshold for no growth is determined (Gth). Fractographic analyses were performed in order to identify the main failure mechanisms related to each joining technology under Mode II. The results indicated an initial cohesive failure followed by an adhesive failure promoted by crack propagation at the interface between the adhesive and the composite adherend on SB and CB samples, through the coalescence of microcracks that promote the adhesive failure process, leading to fiber pull-out from the matrix and cusps formation in the fracture surface. These results explain the low performance behavior observed on SB and CB bonded techniques. It is worth mentioning that the results and behavior observed in this work are valid only for the laminates, adhesives, surface treatment, and environmental conditions tested herein.

© 2022 Elsevier LtdEthanol is a renewable fuel and can be used in electric hybrid vehicles concepts, especially for countries capable of producing such fuel in a sustainable way. A strategy to enhance these concepts is the use of lean-burn combustion, which is an effective way to improve the fuel economy from spark-ignition engines, while obtaining low pollutant emissions. However, these improvements are complicated to achieve in a practical way because lean combustion has low rates of reaction, extinction, and misfire cycles, leading to cyclical variability for the engine operation. The drawback becomes even greater when lean combustion is associated with commercial ethanol fuels and direct injection. Therefore, the objective of the present work is to provide an experimental analysis of spray guided direct injection with commercial fuels used in a consolidated market for the use of ethanol such as the Brazilian one, in particular hydrous ethanol (E95W05) and ethanol-gasoline blends (E27G73). The experiments were conducted in an optically accessible spark-ignition engine and the lean combustion effects on engine cycle variability, performance, flame morphology, and exhaust emissions were assessed. In general, the results indicated that combustion instabilities can be correlated from thermodynamic and optical analyses. Flame instabilities for E95W05 were associated with the lower flame propagation speed caused by the temperature reduction during lean combustion. Additionally, exhaust emissions contained the presence of unburned ethanol which increased when combustion became leaner. Moreover, the lower flame propagation speed was one of the factors responsible for reducing engine performance and increasing combustion variability. The results indicated that vaporization was a relevant phenomenon affecting ethanol combustion in the direct injection mode. The cooling effect of fuel vaporization presented itself as a powerful means for the reduction of NOx and aldehydes, even for the lean operation. Higher emissions of CO and THC were also observed for the engine operating with E95W05 when compared to E27G73. The results of the present work showed that special attention must be paid to the use of commercial fuel with a high ethanol content in spray-guided direct injection engines, especially during lean-burn combustion, in order to not compromise the performance nor increase pollutant emissions.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.Solid propellants are usually characterized by their ballistic and mechanical properties. However, these properties are seldom homogeneous. Processing factors such as multi-batch, casting, curing and post-curing dynamics induce transfer of loads and defects along the propellant. This propellant heterogeneity is responsible for different ballistic and mechanical properties in the grain. This paper presents a novel experimental procedure to characterize the elastic properties of single- and multi-batch solid propellants based on the use of the two-dimensional digital image correlation (DIC) method. The proposed experimental procedure has been applied to two different specimen configurations namely SBIP (single-batch inert propellant) and MBIP (multi-batch inert propellant) propellants. The SBIP specimen was manufactured in a single shot aiming at a more homogeneous mechanical behavior and uniform degree of cure along the propellant length. On the other hand, the MBIP specimen was manufactured in three different stages where each stage has a different degree of cure. Both specimens have a diameter-to-length (L/D) ratio equals to 19, which is an aspect ratio representative of typical large-scale solid-fuel grain rocket configurations. Additionally, in order to validate the in-situ measured properties, tests at small coupon level were also carried out using small cylindrical coupons taken from the same regions of interest used to measure the mechanical properties of the SBIP and MBIP specimens. A very good agreement between the measured local and global (in-situ) strain fields and mechanical properties was found in both testing scales, thus validating the proposed testing procedure based on the DIC technique. Results showed an increase in the elasticity modulus in the specimen bottom due to gravity effects.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.With increasing regulations for pollutant emissions and greenhouse gases on spark-ignition engines, there is a need for improvement on engine fuel efficiency and investment in potential alternate biofuels, such as ethanol. There are several technologies available to increase fuel efficiency in gasoline engines, but further development is still needed for flex-fuel direct injection and ethanol-optimized applications. By operating a research spark-ignition engine with optical access, at partial load and low-speed condition, combustion performance was evaluated by means of cylinder pressure and heat release analysis, along with high-speed cycle-resolved direct visualization of flame propagation. Direct fuel injection (DI) technology was primarily utilized; tests were performed with port fuel injection (PFI) to obtain baseline results for comparison. Commercially available fuel mixtures of hydrous ethanol (95% vol ethanol, 5% vol water) and gasoline-ethanol blend (73% vol gasoline, 27% vol ethanol) were tested. On PFI engine tests, lower cylinder pressures were registered for ethanol due to higher charge cooling effect. Air-guided DI showed higher cyclic variation and delayed combustion for both fuels, related to a combination of less time for fuel vaporization on DI and cylinder wall-wetting, which is undesirable especially emissions-wise. Spray-guided DI presented improvements in rate of burn and cyclic performance over air-guided DI system, in view of a more favorable fuel injector position, enabling better fuel spray development and less wetting of the cylinder wall, despite still occurring impingement over the piston surface. Optical investigations revealed a tendency for gasoline flames to show more center of mass displacement throughout propagation, probably linked to the faster vaporization of gasoline and interaction with in-cylinder air flow. Flame circularity indicated higher values for ethanol on DI operation; this is aligned with other authors’ results but requires further investigation as to completely understand the causes.

© 2022 SAE International. All rights reserved.Restrictions on emissions have been made to guide society into a more sustainable development. The impasse between regulations and the expectation of a growing demand for aviation exposes the need for decarbonization of the sector. In this way, the utilization of hydrogen associated with fuel cells stands out as means to eliminate emissions during flight. This study evaluates the feasibility of using cryogenic liquid hydrogen (LH2) tanks as both energy source and cooling advantage for a small aircraft with electric propulsion. First, a propulsion system powered by a hybrid setup with Proton-Exchange Membrane Fuel Cells (PEMFC) and batteries is proposed for a small aircraft replacing an Internal Combustion Engine (ICE) and fuel tanks. Then, the new powerplant is integrated into the aircraft and simulated using the SUAVE tool. Next, a heat management analysis is performed to assess heat generation within the aircraft and heat requirements in the cryogenic tanks to meet the hydrogen consumption throughout a mission profile. Later, a sensitivity analysis explores the behavior of this heat balance with the variation in cruise duration. It is found that additional cooling capacity is required beyond that the provided by the cryogenic LH2 for this size of aircraft and mission profile, which is proposed as the additional liquid cooling system that was added to the simulation to obtain the final powerplant configuration.

Copyright © 2022 by ASME.The present study aims to evaluate the intrinsic differences in in-cylinder combustion in low load and low-speed conditions by applying experimental and numerical techniques. The experimental apparatus consisted of an AVL5406 SI-PFI single-cylinder with optical access operating under two different fuel delivery methods: Port Fuel Injection (PFI) and Direct fuel Injection (DI) with anhydrous ethanol (E100) and hydrous ethanol (E96W4). The outcomes of the engine-like conditions tests were evaluated based on the quantitative analysis of the flame propagation and on the thermodynamic data obtained using INDICOM. A Video Scope VS4-1845HS high-speed camera providing cycle resolved UV-visible digital image captured the natural emission of the flame for each test. Forthwith image acquisition, the flame propagation characteristics were post-processed through image segmentation techniques. Finally, relevant literature was revised to support the results and findings obtained at this time. The contribution of this study to the internal combustion engines research remains in gathering more information about in-cylinder flame front propagation and combustion stability for E96W4 and E100 ethanol under partial load and stoichiometric and lean conditions.

© 2021, The Author(s).In the last years, fiber-reinforced polymer composites have been under study for additive manufacturing. For this purpose, it is important to assess the behavior of these materials in terms of mechanical properties. The present experimental study evaluates the mechanical resistance of both PLA and carbon fiber reinforced PLA. The work used a full factorial Design of Experiments (108 tests) selecting as factors the infill density, infill pattern, material, number of perimeters and printing orientation. The main results highlight that the most influential factors on the tensile strength are both type of material and number of perimeters. In this study, the use of reinforcements did not improve the mechanical resistance attained by the corresponding virgin material. Particularly, for some selected specimens, the porosity measured in the fracture section is larger for the reinforced PLA specimens, so they showed a smaller cross-section.

© 2022 by the authors. Licensee MDPI, Basel, Switzerland.The present work describes a methodology to compute equivalent volumes representing the microstructure of 3D-printed continuous fiber-reinforced thermoplastics, based on a statistical characterization of the fiber distribution. In contrast to recent work, the methodology herein presented determines the statistically equivalent fiber distribution directly from cross-section micrographs, instead of generating random fiber arrangements. For this purpose, several regions, with different sizes and from different locations, are cropped from main cross-section micrographs and different spatial descriptor functions are adopted to characterize the microstructures in terms of agglomeration and periodicity of the fibers. Detailed information about the adopted spatial descriptors and the algorithm implemented to identify the fiber distribution, as well as to define the location of cropped regions, are given. From the obtained statistical characterization results, the minimum size of the equivalent volume required to be representative of the fiber distribution, which is found in the cross-section micrographs of 3D-printed composite materials, is presented. To support the findings, as well as to demonstrate the effectiveness of the proposed methodology, the homogenized properties are also computed using representative equivalent volumes obtained in the statistical characterization and the results are compared to those experimentally measured, which are available in the literature.

© 2022 Elsevier B.V.This paper presents the results of the Density Functional Theory (DFT) calculations and reactive molecular dynamics (RMD) simulations of the furazanotetrazinedioxide (FTDO) explosive, a novel highly energetic material. The details of the mechanism of the FTDO decomposition have been elucidated for the first time. The calculated activation energy was found to be 30.96 ± 2.25 kJ/mol. The DFT calculation results suggested that FTDO is prone to the fragmentation and decomposition processes. The study results present original mechanisms for the FTDO detonation/decomposition along with the values for the activation energy and frequency factor with high linear determination coefficient.

© 2021 Elsevier LtdThe current work presents the simulation of the pyrolysis and combustion of alternative jet fuels by reactive force field molecular dynamics methods. A comparison has been done between saturated hydrocarbon farnesane and two unsaturated compounds, α-farnesene and β-farnesene, all of them obtained by the fermentation of sugars present in sugarcane juice. The pyrolysis and combustion mechanisms were elucidated for all the three species at a specified temperature. Significant differences have been observed among the compound reactions during the decompositions. Using a first-order approach, the Arrhenius parameters of the global process were obtained with three different temperatures, held constant over time. For the pyrolysis, the obtained activation energies for farnesane, α-farnesene, and β-farnesene were 132.55, 117.28, and 112.88 kJ mol−1, respectively, and for the combustion, the obtained activation energies were 71.63, 37.99, and 37.98 kJ mol−1, respectively. These data are compatible with the results found in the literature for hydrocarbon fuels. A detailed computational study of all three compounds was performed using the B3LYP/6–311 + G(d,p) approach in the gas phase. Analysis of structures, NBO charges, FMOs, MEP plots, and global reactivity parameters unequivocally supports the simulation results obtained using the ReaxFF code, proving noticeably higher potential reactivity of α- and β-farnesenes compared to farnesane, and furthermore higher reactivity of β-farnesene compared to α-farnesene.

© 2021, The Society for Experimental Mechanics, Inc.Piezoelectric materials have been increasingly applied to a wide range of engineering and scientific applications in the past three decades. One application of interest involves wind tunnel testing to quantify and evaluate the aeroelastic behavior of aircraft wings. In this paper, the focus is on the suitability of piezoelectric sensors, namely PVDF (Polyinylidene Fluoride), to quantify the aeroelastic response of wing models by acquiring modal parameters, i.e. the natural frequencies and damping factors of the vibration modes. Concurrently, a complementary goal is to use PZT (Lead Zirconate Titanate) materials as actuators to better excite the vibration modes that are not adequately energized by the aerodynamic flow. During the setup phase of the experimental apparatus, several studies were performed to help define the test parameters. The aeroelastic tests were conducted in a wind tunnel using a single PZT as actuator and a single PVDF as sensor. The modal parameters obtained using a single PVDF sensor response were then compared with those estimated using laser doppler vibrometry. These parameters were then used to estimate the pre-flutter speed, using both sensing techniques, for three case studies with different mass ballast configurations. A very good agreement was observed between the two sensing techniques, when comparing the results in terms of the frequencies and damping factors of the mode shapes leading to flutter. The results show the suitability of using a single PVDF sensor to estimate the modal parameters, in very turbulent and noisy conditions that are characteristic in wind tunnel testing. PZT is found to reduce the exogenous noise caused by the aerodynamic flow when considering a high number of averages.

© 2022, Emerald Publishing Limited.Purpose: While computational methods are prevalent in aircraft conceptual design, recent advances in mechatronics and manufacturing are lowering the cost of practical experiments. Focussing on a relatively simple property, the lift curve, this study aims to increase understanding of how basic aerodynamic characteristics of a complex stealth configuration can be estimated experimentally using low-cost equipment, rapid prototyping methods and remotely piloted aircraft. Design/methodology/approach: Lift curve estimates are obtained from a wind tunnel test of a three-dimensional-printed, 3.8%-scale model of a generic fighter and from flight testing a 14%-scale demonstrator using both a simple and a more advanced identification technique based on neural networks. These results are compared to a computational fluid dynamics study, a panel method and a straightforward, theoretical approach based on radical geometry simplifications. Findings: Besides a good agreement in the linear region, discrepancies at high angles of attack reveal the shortcomings of each method. The remotely piloted model manages to provide consistent results beyond the physical limitations of the wind tunnel although it seems limited by instrumentation capabilities and unmodelled thrust effects. Practical implications: Physical models can, even though low-cost experiments, expand the capabilities of other aerodynamic tools and contribute to reducing uncertainty when other estimations diverge. Originality/value: This study highlights the limitations of commonly used aerodynamic methods and shows how low-cost prototyping and testing can complement or validate other estimations in the early study of a complex configuration.

© 2022 by the authors. Licensee MDPI, Basel, Switzerland.In this paper, a dynamic scaling methodology is introduced to devise reduced scaled models of aircraft with the objectives of minimizing the development cost and exploring the design space. A promising way to accomplish this is using Topology Optimization (TO) for Additive Manufacturing (AM). Here, TO is employed to design a reduce scale model by matching its natural frequencies and mode shapes to those of a full scale model. Different TO strategies based on density approach are tested with the goal of achieving a dynamically scaled structure that can be manufactured. To achieve this goal, the TO solution should be free from intermediate densities, which is observed for some TO strategies but not all. When no penalization factor is applied: (i) the relative difference between natural frequencies is less than 1% and (ii) the estimated Modal Assurance Criteria (MAC) metric to evaluate the correlation between mode shapes is close to the ideal identity matrix. These results demonstrate the effectiveness of the dynamic scaling methodology. However, when using a penalization factor to avoid intermediate densities, the dynamic behavior correlation between full and scaled models degrades. This trend is more visible in the MAC metric, where off-diagonal terms above 20% and diagonal terms below 90% appear.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.With increasing pressure to lower pollutant emissions, the aerospace industry has turned its attention to the design of more efficient aircraft. Electric airplanes are seen as one of the most promising solutions to this problem, and significant investments are being made to develop this type of aircraft. Since the electric propulsion system is distinct from those based on internal combustion engines, the performance characteristics of all-electric airplanes can be significantly different from that of regular aircraft. An important element of this new type of propulsion system, and one of the reasons for its unique characteristics, is the power source. Fuel cells are one of the main embedded power sources employed to provide electricity in vehicles, and its use to power electric airplanes is currently being researched. This work presents an analytical investigation of fuel and oxidizer consumption during the cruise flight of all-electric aircraft powered by fuel cells. This study is relevant because cruise flight usually is the crucial phase that drives aircraft design requirements in what concerns energy requirements. A novel formulation is developed, and parametric models are provided for the airplane relevant systems. New analytical solutions are derived in parametric, closed form, allowing quick calculations and eliminating the need for numerical solvers and possible convergence issues. Also, simulations are provided to illustrate the method developed in the article. The results show that the optimal velocities for minimal consumption can be higher than predicted by conventional methods.

Copyright © (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.There are some approaches for updating models to later model the aeroelastic behavior, and in this work, the Modal Assurance Criterion (MAC) helps identify the parameters. The objective of this work was to update the finite element model for the EOLO aircraft. We used the modal shapes derived from Ground Test Vibration (GVT) as a basis of comparison for the MAC, in addition to using the Nastran software to optimize the stiffness properties of the analytical model of the EOLO aircraft. It noted that the natural frequencies of the updated model approached the GVT data and the cross-correlation improved, but the correlation was far from ideal. Therefore, the model was updated and improved over the initial model.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.Subscale aircraft have been used for decades to design new aircraft and evaluate new design techniques. The acquisition of in-flight data from subscale aircraft is already possible today, such as a manned or fullscale aircraft. Thus, more reliable flight simulators are built for flight quality analysis and control design. This work aims to implement a data acquisition and processing system, with the objective of identifying the complete dynamics of a subscale aircraft, model Cessna 182.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The development of microelectronics combined with the cheapness of manufacturing processes has allowed the construction of subscale models equipped with sensors and control systems equivalent to a real aircraft. This work analyses the Generic Future Fighter (GFF) subscale concept developed by Linköping University under the Future Aircraft Design and Demonstration (FADEMO) project. The GFF subscale is a radio-controlled aircraft with 14% of the size of the full-scale concept aircraft. A Stability Augmentation System (SAS) will be designed to stabilize the longitudinal dynamics for different positions of the c.g., artificially modified for three different positions. Despite the several control techniques currently available, methods such as the Linear Quadratic Regulator (LQR) are still adopted for the stability control of aircraft in flight. However the LQR method present in their classic form, limitations to incorporate performance parameters and operational restrictions in the design phase. A promising alternative to circumvent this problem is the use of Linear Matrix Inequalities (LMIs) as a tool to convert stability and control problems into optimization problems. This work presented an LQR-LMI formulation augmented by D-stability criterion to simplify the determination of a single feedback gain matrix that guarantees the stability and keeps the flight characteristics by varying the c.g. position.

© 2022, American Institute of Aeronautics and Astronautics Inc. All rights reserved.System identification based on mathematical models is generally restricted to linear systems. To model nonlinear behavior, more complex mathematical models are needed and often not available. To model the nonlinear dynamics at high angle of attack of a fighter, a neural network method was applied. The system identification process used in this work used flight test data acquired from a remotely piloted Generic Future Fighter (GFF) subscale. After the application of the neural network, the non-linear effect present in the detachment of the wing boundary layer was possible to estimate. The neural network used was the Feedforward type and the optimization of the parameters was carried out with Backpropagation. Stall maneuvers were initially used to train the neural network (training cycle) and later a new stall maneuver was used to validate the identification (prediction cycle). The method demonstrated the ability to estimate the lift curve in a subscale fighter.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.It is well-known that ice accretion can adversely impact the aerodynamic performance of airfoils and wings. In this work, we conducted an experimental investigation on the impact of different ice shapes on the flow around airfoils. The NACA 23012 and the GLC-305 airfoils were tested at a low-reynolds wind tunnel, which included forces, moments and surface pressure were evaluated, and Particle Image Velocimetry (PIV) was used for flow field measurement. The studied ice type was a simulated single horn based on the glaze ice accreted on airfoil leading edge, with different heights and chord position. The parametric approach was applied in order to vary the ice geometric characteristics. Evaluation was performed with the ice shape extruded throughout the entire span of the airfoil, and the objective of this research was to provide a flowfield-physics perspective on the flow with different ice geometries and its effect on the overall aerodynamic performance of the airfoil under low Reynolds conditions.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Although there are literature references that detail guidelines and flight test techniques for Fixed Wing Air-to-Air Refueling (FWAAR), there are no well established methods to perform Helicopter Air-to-Air Refueling (HAAR). Straightforward application of those FWAAR methods neglecting specific helicopter performance and HQ characteristics did not demonstrate to be a successful approach, given that actual critical conditions for defining HAAR envelope could not be identified. Therefore, this work presents methods and techniques developed by the Brazilian Flight Test and Research Institute (IPEV) during the HAAR qualification process between the helicopter H225M and the tanker KC-130H. Results demonstrated that a more complete assessment for defining HAAR envelope could be performed when using a power margin approach for planning and performing flight tests. Literature CHR (Cooper-Harper Rating Scale) contact tasks for FWAAR based on precision performance criteria were then tailored in order to take into account low closure rate profiles and limited power margins. Additionally, given the limitations of the CHR assessment, a modified version of DIPES (Deck Interface Pilot Effort Scale), which is well-know for multi-axis evaluation in helicopter / ship qualification flight testing, was also applied when performing contact tasks. This approach allowed to identify unacceptable pilot workload levels more easily than the CHR. Therefore, this paper aims at presenting the lessons learned during planning, execution and data processing steps of the HAAR flight test campaigns in order to further enhance flight test techniques on that type of procedure.

© 2022 Elsevier Inc.In recent years, different dispersion-diffusion (eigen)analyses have been developed and used to assess various spectral element methods (SEMs) with regards to accuracy and stability, both of which are very important aspects for under-resolved computations of transitional and turbulent flows. Not surprisingly, eigenanalysis has been used recurrently to probe the inner-workings of SEM-based implicit LES approaches, where numerical dissipation acts alone in lieu of a subgrid model. In this study we present and discuss an intriguing linear mechanism that causes energy transfer across Fourier modes as seen in the energy spectrum of SEM computations. Despite its linear nature, this mechanism has not been considered in eigenanalyses so far, possibly due to its connection to the often overlooked multiple eigencurves feature of periodic eigenanalysis. As we unveil the mechanism in the simplified context of linear advection, we point out how its effects might take place in actual turbulence simulations. In particular, we highlight how taking it into account in eigenanalysis can improve dissipation estimates in wavenumber space, potentially allowing for a superior correlation between dissipation estimates and energy spectra measured in SEM-based eddy-resolving turbulence computations.

© 2022 by the authors.A numerical investigation is proposed to explore the flow past a novel wavy circular cylinder as a passive flow control, whose shape is determined by a sinusoidal function applied to its leading edge line, similar to studies with wavy leading-edge airfoils. The latter are motivated by the wavy-shaped tubercles found in the flippers of humpback whales, which are believed to improve their maneuverability. Our attempt is, therefore, to assess the effects of leading-edge waviness now on a simpler and canonical geometry: circular cylinders. The present work relies on iLES simulations conducted with Nektar++ at a Reynolds number of 3900. Besides the straight cylinder, two wavy geometries are assessed, which are determined by a single wavelength of 37.5% for two amplitudes, 3% and 11%, based on the mean diameter of the wavy cylinder. Our results showed that, contrary to what is usually the case with traditional wavy cylinders at similar Reynolds numbers, waviness caused a reduction in the near-wake recirculation length and an increase in the mean near-wake turbulent kinetic energy compared to the straight cylinder. This was followed by a reduction in base pressure (up to about 36%) leading to a rise in lift oscillations and also to a significant increase in the mean drag coefficient of up to about 28%. An attempt to detail the flow phenomena is provided, evidencing the emergence of counter-rotating pairs of streamwise vortices between peaks. It is argued that the differences observed in recirculation length, turbulent kinetic energy, and force coefficients start even prior to the formation of these coherent structures and end up with interactions with the near wake.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Flow over a humpback whale flippers bio-inspired wavy cylinder is experimentally investigated. Besides the smooth model, a selection of a set of 4 wave combinations (2 amplitudes x 2 wavelengths) is compared using pressure distribution and aerodynamic forces. The study is performed in a wind tunnel at Reynolds numbers ranging from 3.9 × 104 to 2 × 105, within the sub-critical regime. The most notable results show that, for the 12% wavelength, the 3% and 11% amplitudes have opposite effects, with a drag coefficient reduction of up to 25%, and an increase of up to 25%, respectively. Flow visualizations shows the formation of three-dimensional laminar separation bubbles and the action of counter-rotating vortex pairs, with a shift in the separation line and a change in the base pressure, which suggest the mechanisms behind drag variation.

© 2021 Elsevier B.V.One of the strengths of the discontinuous Galerkin (DG) method has been its balance between accuracy and robustness, which stems from DG's intrinsic (upwind) dissipation being biased towards high frequencies/wavenumbers. This is particularly useful in high Reynolds-number flow simulations where limitations on mesh resolution typically lead to potentially unstable under-resolved scales. In continuous Galerkin (CG) discretisations, similar properties are achievable through the addition of artificial diffusion such as spectral vanishing viscosity (SVV). However although SVV is recognised as very useful in CG-based high-fidelity turbulence simulations, this approach has been observed to be sub-optimal when compared to DG at intermediate polynomials orders (P≈3). In this paper we explore an alternative stabilisation approach through the introduction of a continuous interior penalty on the gradient discontinuity at elemental boundaries, which we refer to as a gradient jump penalisation (GJP). Analogous to DG methods, this introduces a penalisation at the elemental interfaces as opposed to the interior element stabilisation of SVV. Detailed eigenanalysis of the GJP approach shows its potential as equivalent (sometimes superior) to DG dissipation and hence superior to previous SVV approaches. Through eigenanalysis, a judicious choice of GJP's P-dependent scaling parameter is made and found to be consistent with previous a-priori error analysis. The favourable properties of the GJP stabilisation approach are also supported by turbulent flow simulations of the incompressible Navier–Stokes equation, as we achieve higher quality flow solutions at P=3 using GJP, whereas SVV performs marginally worse at P=5 with twice as many degrees of freedom in total.

© 2022 John Wiley & Sons, Ltd.Advancements seeking structural components' strength and weight reduction necessarily pass through fatigue testing. Understanding failure phenomena and crack evolution is a way of methodologically achieving such a goal. An own-designed resonant fatigue test rig was used to study the behavior of three distinctly manufactured crankshaft batches. A control system and a resonant frequency estimator were developed to follow the overall stiffness reduction with crack advancement. The control algorithm followed the frequency decay to compensate for the input load. The control strategies were validated by finding the system's natural frequency at the beginning of the test and maintaining a constant nominal load. Fractographies made with failed and non-failed specimens revealed the connection between the expected physical results and the natural frequency shift evolution. The implemented logic enables crack advancement tracking and failure determination. The developments here can be overflown to different resonance fatigue systems to characterize their endurance performance.

© 2021, Korean Society for Precision Engineering.Powder metallurgy represents an alternative to increase sustainability in the manufacturing of automotive gears, but its potential is hindered by a certain lack of knowledge on surface integrity properties that can impair the gear performance. This study explores the effects of the microstructural differences induced by this chain on the residual stress heterogeneity state of gears. X-ray diffraction methods of macro residual stress mapping and line profile analysis were applied for measurements of gear teeth after subsequent steps of the powder metallurgy and the conventional wrought steel chains. The powder metallurgy chain induced more pronounced heterogeneities than the conventional manufacturing, characterized by non-uniform residual stress distributions along the lead and the involute profiles of gear flanks. These non-uniformities observed after carburizing were traced back to the previous steps, surface densification, sintering and compaction. The residual stress distribution patterns of these steps were compatible with the plasticity dynamics of each manufacturing process. Such surface integrity heterogeneities result in a residual stress gradient along the gears functional surface, exposing particular regions to be more susceptible to fatigue effects.

© 2022 The Authors.The evolution of residual stress (RS) induced by laser powder bed fusion (L-PBF) along post-processing steps of automotive carburizing steels is a topic still underexplored by the scientific community. In this study, L-PBF specimens of 20MnCr5 steel produced with different build orientations were subjected to the same stress relief, milling and carburizing steps. RS and the diffractogram full width of half maximum (FWHM) depth profiles obtained through X-ray diffraction were compared along the manufacturing chains. It was shown that the previous manufacturing steps influence the final RS state, from L-PBF to carburizing.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.This work extends the classic lunar patched-conic approximation model for Earth–Moon transfers by adding two complexities: the eccentricity of the Moon’s orbit around Earth and the eccentricity of the terminal orbits. In this way, the initial low Earth orbit (LEO) and the final low Moon orbit (LMO) are assumed elliptic. The transfer trajectory is performed by application of two impulses at the terminal orbits; however, they are not necessarily applied at the pericenter of the terminal orbits (LEO and LMO). The positions of application of the impulses are specified by the values of the true anomalies that define the point of departure in the LEO and the point of arrival in the LMO. The transfer problem is also formulated in the context of the planar elliptic restricted three-body problem with the same complexities: eccentricity of the primaries Earth and Moon, and the eccentricity of the terminal orbits. However, an additional final constraint is added relating the flight path angle of the transfer trajectory and the one of the LMO at the arrival time. In the proposed patched-conic approximation, this constraint does not appear as it is solved geometrically. In both models, a two-point boundary value problem solves the Earth–Moon trajectory. A one-degree-of-freedom problem, which uses the Moon’s position as a parameters, and a two-degree-of- freedom optimization problem, which sets the Moon’s position as an unknown to be solved, are also formulated in both models and solved by the sequential-gradient restoration algorithm. The results show some impossible configurations of arrival at LMO, as well as the agreements between the models. Also, a huge importance in the orientation of the LEO, determined by its argument of pericenter, is observed in the fuel consumption. So, a study of penalty on the fuel consumption due to the use of non-optimal values of argument of pericenter of the LEO is performed.

© 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.The objective of this work is to establish a set of procedures by applying computational tools to find optimal key parameters for the preliminary design of an expendable multistage launch vehicle starting from a specific set of mission requirements. In order to achieve this objective, the decomposition of the problem is made through an evaluation of the main disciplines related to the preliminary design of launch vehicles. Then, through the application of multidisciplinary design optimization methodologies, two solution methods are implemented in this work: the Multiple Subarc Gradient Restoration Algorithm and the Genetic Algorithm. These algorithms solve, respectively, the optimal control problem associated with the flight trajectory and propulsive curve optimization and the optimization problem of solid rocket motors. As an illustration of the method, for the problem proposed, while MSGRA achieved a fast optimization of the trajectory and the thrust profile, GA evaluated a total of 12,000 rocket motor configurations with 1721 Pareto designs achieved. Finally, an extensive analysis is made to the solutions obtained by these algorithms, and a multicriteria decision tool was applied to obtain a feasible two-stage launch vehicle.

© 2022 by the authors.A numerical investigation is proposed to explore the flow past a novel wavy circular cylinder as a passive flow control, whose shape is determined by a sinusoidal function applied to its leading edge line, similar to studies with wavy leading-edge airfoils. The latter are motivated by the wavy-shaped tubercles found in the flippers of humpback whales, which are believed to improve their maneuverability. Our attempt is, therefore, to assess the effects of leading-edge waviness now on a simpler and canonical geometry: circular cylinders. The present work relies on iLES simulations conducted with Nektar++ at a Reynolds number of 3900. Besides the straight cylinder, two wavy geometries are assessed, which are determined by a single wavelength of 37.5% for two amplitudes, 3% and 11%, based on the mean diameter of the wavy cylinder. Our results showed that, contrary to what is usually the case with traditional wavy cylinders at similar Reynolds numbers, waviness caused a reduction in the near-wake recirculation length and an increase in the mean near-wake turbulent kinetic energy compared to the straight cylinder. This was followed by a reduction in base pressure (up to about 36%) leading to a rise in lift oscillations and also to a significant increase in the mean drag coefficient of up to about 28%. An attempt to detail the flow phenomena is provided, evidencing the emergence of counter-rotating pairs of streamwise vortices between peaks. It is argued that the differences observed in recirculation length, turbulent kinetic energy, and force coefficients start even prior to the formation of these coherent structures and end up with interactions with the near wake.

© 2022 International Astronautical Federation, IAF. All rights reserved.A blowdown liquid fuelled rocket engine (LRE) survey, propelled by commercial hydrogen peroxide (CHP) and automotive ethanol, is presented. The main objective of this engine is to have a low-cost technology demonstrator to be used in a prototype of a training rocket for the Alcantara Launch Centre. In a LRE, the injector is an essential component since it is responsible for providing an efficient atomization and a stable burning in the combustion chamber. The complete decomposition of the pure hydrogen peroxide (H2O2) produces gaseous oxygen and water vapor. In this case, the commercial CHP is a 50% H2O2/50% H2O mixture. As there is much water in this mixture, a great part of the decomposition heat is absorbed by the water that remains after the catalytic bed. A crossover occurs at 63-64% mixture, when rapid, accelerated decomposition becomes self-sustaining. Different methods to model two-phase flow on a horizontal pipe have been studied: The homogeneous model, which, in a general fashion, the liquid and gas move at the same velocity; The separated flow model (SFM) that considers that both phases flow separately in the pipes; And the dimensional and similitude analysis. As the studied component is an injector (almost isentropic) composed by different subcomponents, the SFM is used. The sum of the area occupied by each of the phases must be the internal area of the injector, which are determined by the hydraulic diameter of each one (and) and the ratios (and) of the actual cross-section area of flow to the area of the hydraulic diameters. Furthermore, due to the all-transient characteristic of the blowdown, these hydraulic diameters are variable. In order to test and validate this blowdown LRE, a test bench was built using Commercial off-the-shelf (COTS) low-cost equipment compatible with the oxidizer. In addition, pressure transducers were installed to measure relevant data, regarding the decomposition produced, on the oxidizer tank as well as on the input/output of the catalytic bed. The results showed that the SFM is an appropriate solution to model this blowdown LRE and that for an accurate simulation, the Arrhenius parameters of the CHP with the catalyst must be determined by many tests.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Flow over a humpback whale flippers bio-inspired wavy cylinder is experimentally investigated. Besides the smooth model, a selection of a set of 4 wave combinations (2 amplitudes x 2 wavelengths) is compared using pressure distribution and aerodynamic forces. The study is performed in a wind tunnel at Reynolds numbers ranging from 3.9 × 104 to 2 × 105, within the sub-critical regime. The most notable results show that, for the 12% wavelength, the 3% and 11% amplitudes have opposite effects, with a drag coefficient reduction of up to 25%, and an increase of up to 25%, respectively. Flow visualizations shows the formation of three-dimensional laminar separation bubbles and the action of counter-rotating vortex pairs, with a shift in the separation line and a change in the base pressure, which suggest the mechanisms behind drag variation.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.An aircraft flying under icing conditions tends to accumulate ice on aerodynamic surfaces which deteriorates aircraft performance and may affect safety. Recent work obtained, via 3D-scanning, high-fidelity characterization of ice shapes generated in the NASA-CRM model swept wing in the NASA IRT icing wind tunnel. These shapes are highly three-dimensional and in order to better understand and isolate the effects of the three-dimensional parameters, various simplified shapes were built and tested in aerodynamic wind tunnels to compare the results with the high-fidelity representation. Even with this geometrical break-down, the aerodynamic phenomena that takes place in the highly swept wing of the NASA-CRM model are complex. The present work takes a step backwards in the complexity level, evaluating the threedimensional shapes effect on NACA 23012 airfoil, to provide basis for a better understanding of the NASA-CRM icing tests. The effects of horn ice shapes with different spanwise gaps sizes and orientations were evaluated by testing artificial ice shapes on the leading edge of a NACA 23012 airfoil under low-Reynolds-number conditions. The lift, drag, pitching moment and pressure distribution were measured for the clean airfoil and six ice shapes built. The aerodynamic performance and PIV measurements for each of these geometries are compared with its extruded 2D counterpart and clean airfoil configuration. The results regarding the size of the gaps in the ice shapes, showed that the increase in the gap widths directly improved airfoil performance. The PIV flow fields helped identify flow reattachment downstream the horn bubble for ice shapes with gaps. The surface oil visualization for the oriented ice shapes helped understand certain patterns and influence of the cross flow past the horn.

© 2022, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.It is well-known that ice accretion can adversely impact the aerodynamic performance of airfoils and wings. In this work, we conducted an experimental investigation on the impact of different ice shapes on the flow around airfoils. The NACA 23012 and the GLC-305 airfoils were tested at a low-reynolds wind tunnel, which included forces, moments and surface pressure were evaluated, and Particle Image Velocimetry (PIV) was used for flow field measurement. The studied ice type was a simulated single horn based on the glaze ice accreted on airfoil leading edge, with different heights and chord position. The parametric approach was applied in order to vary the ice geometric characteristics. Evaluation was performed with the ice shape extruded throughout the entire span of the airfoil, and the objective of this research was to provide a flowfield-physics perspective on the flow with different ice geometries and its effect on the overall aerodynamic performance of the airfoil under low Reynolds conditions.

© (2022) by International Council of Aeronautical Sciences (ICAS) All rights reserved.Distributed propulsion (DP) is not a new concept but recent advances in electric motors and batteries, along with the need for more environmentally friendly products, brought this concept back to the spotlight. This paper addresses two types of DP: wingtip-mounted propellers and distributed propellers along the wingspan. The benchmark of the analysis is NASA’s X-57 "Maxwell" demonstrator. Another goal of this paper is to evaluate how good is the VSPAERO code to modeling aerodynamic flows, from a simple case of the isolated wing to a more complex 14 rotors case. The overall results show that VSPAERO provides good estimations for most cases.

© 2022 Author(s).Floating offshore wind turbines (FOWTs) are subjected to platform motion induced by wind and wave loads. The oscillatory movement trigger vortex instabilities, modifying the wake structure and influencing the flow reaching downstream wind turbines. In this work, the wake of a FOWT is analyzed by means of numerical simulations and a comparison with linear stability theory. Two simplified models based on the stability of vortices are developed for all degrees of freedom of turbine motion. In our numerical simulations, the wind turbine blades are modeled as actuator lines and a spectral-element method with low dispersion and dissipation is employed to study the evolution of the perturbations. The turbine motion excites vortex instability modes predicted by the linear stability of helical vortices. The flow structures that are formed in the non-linear regime are a consequence of the growth of these modes and preserve some of the characteristics that can be explained and predicted by the linear theory. The number of vortices that interact and the growth rate of disturbances are well predicted by a simple stability model of a two-dimensional row of vortices. For all types of motion, the highest growth rate is observed when the frequency of motion is one and a half the frequency of rotation of the turbine that induces the out-of-phase vortex pairing mechanism. For lower frequencies of motion, several vortices coalesce to form large flow structures, which cause the high amplitude of oscillations in the streamwise velocities, which may increase fatigue or induce high amplitude motion on downstream turbines.