© 2025 The Author(s)Assessing the bending response of infiltrated reinforcement fabrics is crucial in wet compression molding (WCM) as it affects macroscopic wrinkling. Binder-stabilized fabrics may be used in WCM to improve handleability and reduce defects, necessitating their characterization. This study examines the bending behavior of an infiltrated binder-stabilized carbon fiber unidirectional non-crimp fabric (UD-NCF), focusing on the effects of viscosity, loading rate, and binder pre-activation. Infiltration reduces bending stiffness compared to dry fabric owing to lubrication and lower tow-stitch friction, while higher loading rates increase bending stiffness for all considered conditions. Moreover, binder pre-activation increases fabric stiffness by enhancing tow-stitch cohesion and friction. As the first investigation on infiltrated binder-stabilized UD-NCF bending, this work advances understanding of the complex bending response.

© 2025 Elsevier Ltd.The dynamics of hanging chains, a topic studied since the 18th century, has relevance in contemporary engineering applications, particularly in low-frequency vibration control. This paper concerns the use of hanging chains to mitigate vibrations of a host structure. To enable predictions to be made and to identify the key parameters of the chain, four models are developed, each of which contributes to the predictions and physical insight in a different way. The first is a continuous model, which is only strictly valid at relatively low frequencies, when the length of a chain link is small compared to the wavelength at the top of the chain. The second is a finite element model considering a chain made of discrete rigid links, which is valid up to much higher frequencies. The other two models are an approximate hybrid lumped parameter/continuous model, which provides some additional physical insight, and a very simple approximate lumped parameter model, which can be used to predict the vibration attenuation effectiveness of a chain when connected to a host structure. Laboratory measurements are presented to assess the validity of the models and to demonstrate the efficacy of chains as a passive vibration control device.

© 2025 Elsevier Masson SASThe increasing demand for ultrafast aerospace transportation and high-performance strategic systems has fueled the interest in air-breathing hypersonic vehicles. However, their design still presents considerable challenges owing to the tight coupling between the thermodynamic and flight dynamic phenomena. This study proposes an integrated simulation framework capable of representing the coupled behavior of a six-degree-of-freedom hypersonic vehicle and a multi-stage scramjet engine model. The proposed framework incorporates atmospheric variation, aerodynamic and mass models, actuator dynamics, and energy-based thrust modeling under transient conditions. The objective was to evaluate the dynamic and thermodynamic responses of a vehicle during flight maneuvers. To that end, several scenarios were simulated, including descent and transition to level flight, acceleration and deceleration. The results demonstrate that the model captures the strong transients associated with ignition, control response, and inlet compression modulation. Thermodynamic analysis revealed consistent heat transfer, irreversibility, and exergy trends, with the combustion stages being the main source of entropy generation. The propulsive efficiency and specific impulse evolve coherently with thrust demand and flight conditions, whereas control logic successfully stabilizes critical thermodynamic parameters during maneuvering. These findings validate the capacity of the framework to reproduce the coupled dynamics of scramjet-powered hypersonic flights, providing a solid basis for future studies on optimization and thermodynamic analysis.

© 2025 Acta Materialia Inc.High solidification rates and in situ heat treatments are commonly found in additive manufacturing (AM) of steels, resulting in a complex and far-from-equilibrium microstructure. Therefore, standard post-processing heat treatments commonly applied to wrought steels can favor the occurrence of different phenomena and can change the phase transformation sequence, due to the unique microstructure obtained by powder bed fusion – laser beam (PBF-LB). This work reports the microstructural evolution of 15-5 precipitation hardening (PH) stainless steel manufactured by PBF-LB during direct aging heat treatments at 621 °C (AMS H1150 standard condition), a route used to increase fracture toughness due to the martensite reversion and precipitates coarsening. The reversion of martensite into a Ni-rich austenite, predicted by kinetic calculations, was confirmed by high-energy X-ray diffraction (HE-XRD), being preferentially nucleated close to the copper-rich precipitates (CRPs), which can act as a preferential nucleation site. CRPs presented an oval shape, as confirmed by electronic microscopy (SEM and TEM) and atom probe tomography (APT). Fast Fourier transform (FFT) analysis of high-resolution TEM (HR-TEM) images suggests CRPs still present the metastable untwined 3R-type structure after 8 h, rather than the most stable FCC structure. The presence of retained austenite, inherent to PBF-LB-processed PH steels, affects the CRPs evolution in different phases, and the CRPs themselves act as nucleation sites for Nb(C,N) secondary precipitation. These findings emphasize the necessity of microstructure-oriented heat treatment routes to unlock the full potential of additively manufactured PH stainless steels.

© 2025 Elsevier LtdThis study explores the thermal behavior and volatilization kinetics of JET A-1 aviation kerosene and Farnesane, a sustainable aviation fuel compound, and their blend through thermogravimetric analysis in an oxidative atmosphere. For such, experiments were conducted under a synthetic air atmosphere at three different heating rates (10, 15, and 20 ℃ min−1), and results showed that Farnesane exhibits high thermal stability up to approximately 80 °C, followed by rapid decomposition, whereas JET A-1 starts decomposing at 35 °C and volatilizes gradually until reaching 109 °C. The minimum energy required for the volatilization process of Farnesane to start taking place is about four times greater than that for JET A-1, i.e. 53.72 KJ mol−1 and 12.67 KJ mol−1, respectively. Activation energy of 8.88 KJ mol−1 was found for the Farnesane-JET A-1 blend, which is a lower than that for pure kerosene, thus revealing a beneficial and synergistic effect between them, which should ease the initial stages of fuel vaporization, since it is of paramount relevance for efficient combustion.

© 2025 Elsevier B.V.The increase in the production of Sustainable Aviation Fuels (SAFs) is essential to promote the decarbonisation of the aviation sector by 2050. In this study, Raman spectroscopy was used as a tool to investigate structural changes in samples of JET A-1, Farnesane, and a 10 % Farnesane blend with JET A-1(designated FarnJET10), exposed to an oxidative atmosphere for 3, 24, and 48 h. The results show that JET A-1 exhibits higher oxidative stability, while Farnesane is prone to degradation, with a rapid decrease in vibrational band intensity across all regions of the spectrum. The FarnJET10 blend exhibited intermediate oxidative behaviour, but the findings indicate that the presence of Farnesane compromises the stability of JET A-1. Principal Component Analysis (PCA) was applied to distinguish the stability and chemical behaviour of the fuel samples. The first two principal components explained 98.91 % of the total spectral variation, with PC1 and PC2 accounting for 85.44 % and 13.47 %, respectively. The PCA scores demonstrated a clear separation between the pure fuels and the blend, highlighting the distinct oxidative responses and structural changes induced by exposure to an oxidising atmosphere. These findings highlight the oxidative vulnerability of the SAF/fossil fuel blend and its effects on fuel stability, which may compromise performance during storage and operational use in aviation systems.

© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.The present paper presents a systematic approach to quantify the uncertainties when the piezoelectric shunt damping technique is employed to attenuate the vibration effect in arbitrary thin shell structure. The research used an experimental approach. The experimental apparatus employed in the present research was able to analyze the effectiveness of the piezoelectric vibration absorber when applied to a mechanical structure with arbitrary shape, typically used in automotive outer structures. The inherent variability typically found in an automotive body structure assembly and the tolerances of electronic circuits were taken into the account in the analysis. Then, the uncertainty propagation was studied in details for the mechanical structure, RL-shunt circuit, and piezoelectric vibration absorber working in the peak attenuation and in the frequency band. A large dispersion can be observed in the mechanical structure, with a variability of approximately 16 Hz for the natural frequency and 10 dB for the mobility peak amplitude. The piezoelectric capacitance had demonstrated discrepancies from 10 to 27%, in the experimental results. Finally, the experimental uncertainty propagation had demonstrated, when the piezoelectric shunt damping technique is employed, an overall average value of the peak attenuation of 6.25 dB, representing an effectiveness loss of approximately 32%, with a huge variability (standard deviation of 2.1 dB). Considering the frequency range of operation from 190 to 210 Hz, an attenuation of 2.2 dB was achieved in average, in an independent way from the mechanical structure resonant natural frequency.

© 2024 Elsevier LtdStructural members, such as stiffeners, are crucial in aeronautical structures, providing essential dynamic stiffness. However, variability introduced by manufacturing and assembly processes, as well as material inconsistencies, can lead to uncertainties in structural performance. It is crucial to incorporate these uncertainties into structural analysis to ensure reliable design. This paper utilizes the Stochastic Finite Element Method (SFEM) to address uncertainties in typical structural members used in aeronautics. The Perturbation Technique, based on Taylor series expansions, was employed to model uncertainties in aircraft stiffeners. The study focuses on natural frequencies and modal analysis to evaluate the impact of uncertainties on beams with hat and Z sections, commonly used as stiffeners in aircraft panels. These stiffeners were modeled using the Timoshenko beam theory, and sensitivity analysis was performed to identify key contributors to variability. The perturbation parameter was validated through Monte Carlo simulations. Sensitivity analysis, employing gradient-based methods, identified significant factors affecting variability in natural frequencies. A different perturbation parameter was necessary based on the stiffener's geometry: thickness variations required a perturbation parameter on the order of 10−3, whereas dimensions changes in the flange and height required parameters on the order of 10−2. These results underscore the importance of choosing appropriate perturbation magnitudes to avoid inaccuracies in the deterministic frequency response. Once a perturbation parameter is established, it can be applied to similar regions, ensuring the robustness of the SFEM methodology in analyzing the dynamic response of aeronautical structural reinforcements.

© The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2025.A device apparatus was designed and built to enable the testing of sheet metal undergoing cyclic forward and reverse tension–compression loads under plastic deformation, while preventing the specimen from buckling. This test allows the identification of parameters for the characterization of the material according to advanced hardening models, that are of utmost interest to the automotive industry, for accurate representation of the physical phenomena occurring during mechanical forming, which enables for tighter manufacturing tolerances. The test specimens were manufactured from steel sheets made of materials BH220 and DP600, with thicknesses of 0.65 mm and 1.00 mm respectively. For each specimen tested, three tension–compression cycles were performed, at a strain rate of 0.5 mm/min. The maximum displacements were 0.6 mm in tension and 0.6 mm in compression. A fork configuration was used in which the device has four main plate blocks to transmit the longitudinal displacement of the machine to the sheet metal and to restrict the plane transverse displacement. The results show that the device is capable of creating the cyclic stress–strain curve of which accurate parameters of Yoshida-Uemori model can be extracted.

© 2024Identifying the occurrence of gear contact fatigue failure as early as possible is essential for condition-based maintenance (CBM). Vibration signals can be used to identify gear contact fatigue. However, the use of vibration signals can be challenging due to its complexity, compounded by lower levels of vibration during the initial stages of contact fatigue. The present study details a new algorithm that integrates stand-alone features to correlate the vibrational signal with early failure occurrence. The study aim is to identify the failure in the early stages, before reaching the ISO 6336–5 stopping criterion of 4 % damaged area. A damage induction on the flank of helical gears is applied to simulate and characterize the failure occurrence. Damping characteristics with impact evaluation, Kurtosis analysis and the monitoring of the Gear Meshing Frequency are applied to characterize the failure signature. This strategy stands out by the integration of these stand-alone features and their behavior. The algorithm's capacity is verified through durability tests, promoting the natural evolution of this failure mode. Results show a success rate of above 80 % at identifying the failure presence before the stopping criterion limit.

© 2024 Elsevier LtdA composite beam finite element is designed to capture through-thickness effects, specifically normal stress and strain and transverse shear, in the context of geometrically nonlinear analyses. The starting point for the formulation is a similar element already proposed for linear analyzes based on a global–local superposition approach, where local functions are defined in each layer of the laminate, and global functions are defined along the thickness. The consistency of the kinematic hypotheses is guaranteed by imposing the continuity equations of displacements through the thickness, the force balance equations along the thickness, directly or indirectly, by imposing the continuity of transverse stresses, and by applying the boundary conditions on the lower and upper surfaces of the elements. In the context of nonlinear analyzes, the imposition of continuity of displacements is straightforward. However, the continuity of the transverse stresses needs to be carefully imposed, as the relevant stresses are the second order Piola-Kirchhoff stresses and the strains are the Green-Lagrange strains, consistent with the total Lagrangian approach used. The constitutive equations are written in incremental form and a detailed analysis is conducted to ensure that the stresses and strains involved are physically consistent across the different reference frames employed. In order to assess the accuracy of the numerical model implemented, a unique semi-analytical technique is developed to obtain the response of asymmetrical laminated beams under compression.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This study investigates the feasibility of hybrid-electric propulsion for regional aircraft operating in Brazil, using real-world data from Azul Conecta, a subsidiary of Azul Brazilian Airlines. The analysis supports the company’s decision to acquire retrofit hybridization kits from Ampaire by providing technical, operational, and sustainability assessments tailored to its route network. A validated performance model of the Cessna Grand Caravan EX was integrated into the FAST-OAD-CS23HE framework to simulate different mission lengths and hybridization levels. To properly capture the economic impact of environmental gains, this work introduces the Sustainable Direct Operating Cost (DOCSA), a novel metric that accounts for monetized carbon credits in the total cost evaluation. Under this framework, propulsion alternatives are assessed not only by their raw DOC, but also by their effective cost after environmental externalities are internalized. For example, at a 500-nm mission with a 450-kWhybrid configuration, the conventional DOC is reduced by approximately 1.2%, while the SA-DOC shows a reduction of 11.9% when carbon credit revenues are considered. The use of Sustainable Aviation Fuel (SAF) demonstrated the highest decarbonization potential, achieving up to 71% CO2 reduction without any payload penalty. The findings contribute to both strategic fleet planning and the development of public policies to incentivize low-emission aviation through carbon market integration.

© 2025 The Author(s)At the heart of electrocatalyst design and development lies the concept of active sites that are usually identified as those sites for adsorption where the conversion of interest occurs. However, electrochemical interfaces are complex systems where the exact structure and dynamics of interfacial species during a reaction greatly depend on the local reactive microenvironment, including co-adsorbates and solvent molecules, that may include structural transformations upon adsorption, the charge-transfer dynamics, and/or the x,y charge-induced electric field distribution. We review the concept of active sites in electrocatalysis within these lines in light of recent studies that point out the necessity to expand the still widely spread idea of quasi-static atomic-scale sites toward the picture of a dynamically reactive microenvironment: the active site can extend over several tens on nanometers due to surface structural transformations during the reaction, includes interdependent components such as electrode and electrolyte as well as target reactant geometric and electronic structures, and often spontaneously rearranges during the electrocatalytic reaction. Thus, to define optimal reactions conditions, the reactive microenvironment as a whole needs to be considered.

© The Author(s) 2025.The reuse of powder in laser powder bed fusion offers a promising approach to optimizing material usage, reducing costs, and improving sustainability. However, its application in the aeronautical sector presents significant challenges due to strict certification requirements, process reliability concerns, and the need to maintain mechanical integrity over multiple reuse cycles. This study conducts a comprehensive and global analysis of powder reuse, considering its mechanical, economic, and environmental impacts. The methodology includes powder characterization, mechanical testing, cost modelling, and environmental life-cycle assessment, providing a holistic understanding of powder degradation and its implications. Results confirm that successive reuse cycles lead to minor changes in powder morphology and an increase in oxygen content, yet mechanical properties remain within acceptable limits, with a slight improvement in tensile strength. Economically, powder reuse significantly reduces costs, with a 33% decrease observed after a single reuse cycle and further reductions in subsequent cycles. Environmentally, the life-cycle assessment highlights substantial benefits, including a dramatic reduction in material waste, energy consumption, and carbon footprint, reinforcing the sustainability advantages of controlled powder reuse. These findings validate the feasibility of powder reuse in industrial-scale additive manufacturing. The study highlights the importance of implementing standardized reuse protocols to ensure consistency in mechanical properties, minimize variations in powder characteristics, and maintain process stability over multiple reuse cycles. Additionally, it underscores the need for further research into long-term powder recycling strategies, including controlled rejuvenation methods, advanced monitoring techniques, and predictive models for powder degradation. By optimizing reuse practices, industries can maximize cost savings, enhance material sustainability, and significantly reduce the environmental impact of additive manufacturing processes, reinforcing the viability of AM as a competitive and responsible manufacturing approach.

© The Author(s) 2025.Additive manufacturing is nowadays an alternative to traditional manufacturing in the aeronautical sector due to its potential for weight reduction. This research work was developed with data and case studies from an aircraft manufacturer and presents a holistic evaluation of the potential of additive manufacturing regarding, not only technical performance but also cost reduction and environmental sustainability including the use phase of an aircraft. The findings demonstrate that AM can significantly lower life-cycle costs for components with high criticality, achieving up to a 39% reduction compared to traditional manufacturing, even for parts with simple design requirements. This analysis underscores the importance of incorporating post-processing considerations, which account for 13% of the life cycle cost, into both economic and environmental models to ensure informed decision-making. Finally, this study also highlights the importance of optimizing printing strategies as different orientations can influence manufacturing costs.

© 2025 Emerald Publishing LimitedPurpose – This paper aims to assess the feasibility of using additive manufacturing (AM) to produce a gas-turbine’s fuel swirler, thereby validating its suitability for this fabrication process. This study involves a statistical comparison of the AM process with other manufacturing methods, utilizing a multi-criteria decision-making approach to determine the most favorable method for the component. This study also includes the manufacturing of the component and an evolution of the quality control results to ascertain the component’s compliance with required standards. Design/methodology/approach – To compare the different fabrication methods, this paper uses the analytic hierarchy process to compare AM with alternative manufacturing processes, generating different scenarios for comparison. In addition, two samples of the component were additively manufactured to assess their suitability for application in a small gas turbine. Findings – The results indicate that AM was identified as eligible and adequate process for producing the fuel swirler in most scenarios. This study includes the results of a nondestructive quality control process and provides a comprehensive discussion aiming to optimize the component’s quality. These results support the potential for scaling up the production of this component and identifying other components that may benefit from AM. Originality/value – This research contributes to the advancement of technical knowledge regarding the application of an innovative manufacturing method for jet engine components. It aims to enhance manufacturing capabilities for different thermal machine parts while reducing design costs.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Adaptive refinement methods can help speed up expensive simulations by reducing the amount of user-dependent processes during mesh generation. One of the most crucial steps in these methods is identifying regions requiring spatial resolution interventions. One of the most straightforward ways of doing this is using featured-based indicators. Because of their general simplistic nature, they may be inefficient in detecting problematic elements under specific numerical circumstances. The current work seeks to analyze these indicators in the context of spectral/hp discretization using continuous Galerkin. We categorized the indicators into three groups: jump, spectral, and error-based. The first two had their performance tested, while the last was employed as a reference. We analyzed them using multiple one-dimensional and one two-dimensional tests to verify how different feature-based indicators perform in distinct numerical circumstances. To measure their performance, we analyze their capability to decrease discretization error when guiding a sequence of p-adaptation cycles. The indicator that performed most consistently well was based on the maximum derivative jump.

© 2025 The Author(s).We study the hydrodynamic and acoustic fields of turbulent jets issuing from nozzles modified by the addition of cylindrical tabs on the inner surface, one diameter upstream of the exit. The tabs are designed to promote significant growth of steady streaks in the nozzle turbulent boundary layer. A baseline smooth nozzle is also studied for comparison. Acoustic measurements are made using an azimuthal array for Mach numbers in the range 0.4 0.9. The tabs are found to reduce the emitted sound levels by up to 3 dB/St. In terms of overall sound pressure levels, reductions of up to 3 dB are observed at all measured polar angles in the range 20° 90°. Time-resolved particle image velocimetry experiments are conducted to measure the three components of velocity for a series of cross-stream planes at 0.7. A Floquet-based Fourier decomposition is applied for the azimuthally periodic flow field, and spectral proper orthogonal decomposition is then employed to extract coherent structures. Comparison of the structures obtained for nozzles with and without tabs shows an enhancement of the streaky structures by the tabs and a damping of Kelvin-Helmholtz wavepackets. A linear model based on the one-way Navier-Stokes equations is employed to explore the underlying amplification mechanisms and how these are impacted by the tabs. The model reproduces the growth-attenuation mechanism observed in the data, showing that the changes in the mean flow induced by the streaks work to reduce the amplification of the noise-generating coherent structures associated with linear spatial growth mechanisms.

© The Author(s), 2025. Published by Cambridge University Press.This work investigates the receptivity mechanisms of a NACA0008 airfoil to a level of free-stream turbulence (FST) through a direct numerical simulation (DNS) and an associated linearised simulation on the same mesh. By comparing velocity perturbation fields between the two simulations, the study reveals that the streaky structures that degenerate into turbulent spots are predominantly influenced by nonlinear convective terms, rather than the linear amplification of inflow perturbations around the laminar base flow. A power spectral analysis shows differences in the energy distribution between the DNS and linearised simulation, with the DNS containing more energy at higher wavenumbers, for structures located near the airfoil's leading edge. Representative wavenumbers are identified through modal analysis, revealing a dynamics dominated by streak-like structures. The study employs the Nek5000 numerical solver to distinguish between linear and nonlinear receptivity mechanisms over the NACA0008 airfoil, highlighting their respective contributions to the amplification of perturbations inside the boundary layer. In the high FST case studied, it is observed that the energy of the incoming turbulence is continuously transferred into the boundary layer along the length of the wing. The nonlinear interactions generate streaks with higher spanwise wavenumbers compared with those observed in purely linearised simulations. These thinner streaks align with the spanwise scales identified as susceptible to secondary instabilities. Finally, the procedures presented here generalise the workflow of previous works, allowing for the assessment of receptivity for simulations with arbitrary mesh geometries.

©2025 American Physical SocietyThis study investigates the two- and three-dimensional convective and absolute instability characteristics of planar viscoelastic jet flows using the Oldroyd-B and Giesekus models. Analyzing instability in different types of flows is fundamental for understanding their behavior in various natural and industrial applications. Convective instability refers to disturbances that propagate and grow downstream, while absolute instability involves disturbances that grow over time regardless of their position in the flow. Understanding these phenomena can help optimize industrial processes and predict complex flow behaviors, for example. Results indicate that concerning convective instability, the Giesekus model exhibits a larger unstable region compared to the Oldroyd-B and Newtonian models. On the other hand, the Oldroyd-B model is more susceptible to absolute instability than the Giesekus model. Notably, in the Giesekus model, the mobility parameter αG significantly influences the occurrence of absolute instability, which only occurs for small values of αG, for which the fluid tends to the Oldroyd-B behavior. For the tested parameters, only low values of αG (close to the Oldroyd-B model, which corresponds to αG = 0) led to the emergence of absolute instability, while larger values did not. These observations apply to both two-dimensional and three-dimensional disturbances.

© The Author(s), 2025. Published by Cambridge University Press.This paper presents an experimental application of reactive control to jet installation noise based on destructive interference. The work is motivated by the success of previous studies in applying this control approach to mixing layers (Sasaki et al. Theor. 2018b Comput. Fluid Dyn. 32, 765-788), boundary layers (Brito et al. 2021 Exp. Fluids 62, 1-13; Audiffred et al. 2023 Phys. Rev. Fluids 8, 073902), flow over a backward-facing step (Martini et al. 2022 J. Fluid Mech. 937, A19) and, more recently, to turbulent jets (Maia et al. 2021 Phys. Rev. Fluids 6, 123901; Maia et al. 2022 Phys. Rev. Fluids 7, 033903; Audiffred et al. 2024b J. Fluid Mech. 994, A15). We exploit the fact that jet-surface interaction noise is underpinned by wavepackets that can be modelled in a linear framework and develop a linear control strategy where piezoelectric actuators situated at the edge of a scattering surface are driven in real time by sensor measurements in the near field of the jet, the objective being to reduce noise radiated in the acoustic field. The control mechanism involves imposition of an anti-dipole at the trailing edge to cancel the scattering dipole that arises due to an incident wavepacket perturbation. We explore two different control strategies: (i) the inverse feed-forward approach, where causality is imposed by truncating the control kernel, and (ii) the Wiener-Hopf approach, where causality is optimally enforced in building the control kernel. We show that the Wiener-Hopf approach has better performance than that obtained using the truncated inverse feed-forward kernel. We also explore different positions of the near-field sensors and show that control performance is better for sensors installed for streamwise positions downstream in the jet plume, where the signature of hydrodynamic wavepacket is better captured by the sensors. Broadband noise reductions of up to 50 % are achieved.

© The Author(s), 2025. Published by Cambridge University Press. This is an Open Access article,In a combined experimental and numerical effort, we investigate the generation and reduction of airfoil tonal noise. The means of noise control are streak generators in the form of cylindrical roughness elements. These elements are placed periodically along the span of the airfoil at the mid-chord streamwise position. Experiments are performed for a wide range of Reynolds numbers and angles of attack in a companion work (Alva et al., AIAA Aviation Forum, 2023). In the present work, we concentrate on numerical investigations for a further investigation of selected cases. We have performed wall-resolved large-eddy simulations for a NACA 0012 airfoil at zero angle of attack and Mach 0.3. Two Reynolds numbers (0.8 × 105 and 1.0 × 105) have been investigated, showing acoustic results consistent with experiments at the same Reynolds but lower Mach numbers. Roughness elements attenuate tones in the acoustic field and, for the higher Reynolds number, suppress them. Through Fourier decomposition and spectral proper orthogonal decomposition analysis of streamwise velocity data, dominating structures have been identified. Further, the coupling between the structures generated by the surface roughness and the instability modes (Kelvin–Helmholtz) of the shear layer has been identified through stability analysis, suggesting stabilisation mechanisms by which the sound generation by the airfoil is reduced by the roughness elements.

© The Author(s), 2025. Published by Cambridge University Press.We explore a reduced-order model (ROM) of plane Couette flow with a view to performing near-wall turbulence control. The ROM is derived through Galerkin projections of the incompressible Navier–Stokes system onto a basis of controllability modes. Such ROMs were found to reproduce key aspects of turbulence dynamics in Couette flow with only a few hundred degrees of freedom, and here we use them to devise a control strategy. We consider a ROM with an extra forcing term whose structure is given by a combination of eigenfunctions of a linear viscous diffusion equation, optimised in order to minimise the total fluctuation energy. The optimisation is performed at Reynolds numbers Re = 1000, 2000, 3000, and produces a novel control mechanism wherein the optimal forcing leads the flow to laminarisation in all cases. The forcing acts by reducing the shear in a large portion of the channel, hindering the main energy input mechanism. The forced flow possesses a new laminar solution which is linearly stable at Re = 1000 and unstable at higher Re, but whose transient growth of streaky structures is substantially lower than that of laminar Couette flow, leading the flow to full laminarisation when the forcing is removed. Forcings optimised in the ROM are subsequently applied in direct numerical simulations (DNS). The same control mechanisms are observed in the DNS, where laminarisation is also achieved. We show that the ROMs provide an effective framework to design turbulence control strategies, despite the high degree of truncation, which opens up interesting possibilities for turbulence control.

© 2025 Acoustical Society of America.This study explores the use of parabolized stability equations (PSEs) for predicting sound propagation in ducts, a novel application in computational duct acoustics. The PSE, formulated in a general duct-fitted coordinate system, was validated against several test cases, including uniform flow, axial temperature gradients, and laminar/turbulent flows, demonstrating close agreement with existing literature. This paper highlights limitations of the PSE, particularly when the local Helmholtz number decreases, potentially causing mode cutoff, and suggests remedies for mitigating phase and amplitude errors. The efficiency of the PSE is further demonstrated through a comparison with linearized Euler equations for forward fan noise propagation in a turbofan inlet, showing 75.8% reduced computational time and 98.2% reduced memory usage. These computational advantages become more significant as problem size increases, with the PSE outperforming traditional finite element and parabolic approximation methods, especially in cases involving viscous shear flow effects. This makes the PSE particularly well-suited for applications such as boundary layer shielding and liner-boundary layer interactions. The study provides a promising avenue for future acoustic research and practical engineering applications, emphasizing the efficiency and accuracy of PSE in complex duct acoustics.

© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.This work aims to provide a more complete understanding of the resonance mechanisms that occur in turbulent jets at high subsonic Mach number, as shown by Towne et al. (J. Fluid Mech., vol. 825, 2017, pp. 1113-1152). Resonance was suggested by that study to exist between upstream- and downstream-travelling guided waves. Five possible resonance mechanisms were postulated, each involving different families of guided waves that reflect in the nozzle exit plane and at a number of downstream turning points. However, that study did not identify which of the five resonance mechanisms underpin the observed spectral peaks. In this work, the waves underpinning resonance are identified via a biorthogonal projection of Large Eddy Simulation data on eigenbases provided by a locally parallel linear stability analysis. Two of the five scenarios postulated by Towne et al. are thus confirmed to exist in the turbulent jet. The reflection-coefficients in the nozzle exit and turning-point planes are, furthermore, identified. Such information is required as input for simplified resonance-modelling strategies such as developed in Jordan et al. (J. Fluid Mech., vol. 853, 2018, pp. 333-358) for jet-edge resonance, and in Mancinelli et al. (Exp. Fluids, vol. 60, 2019, pp. 1-9) for supersonic screech.

© 2025 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The Actuator Line Method (ALM) is a technique that replaces the detailed airfoil geometry with distributed body forces to predict the flow field. ALM has been widely employed for simulating rotating blade wakes due to its flexibility and accuracy in the far field. In this study, the applicability of ALM for unsteady aerodynamics and acoustic field prediction is evaluated. The case study considered is the harmonic transverse oscillation of a thin airfoil in uniform flow. The ALM body forces are distributed over a few grid points following a Gaussian function, with a range of smearing ratio of ε/c (smearing parameter over the chord length) between 0.4 and 1. These forces are computed using thin airfoil theory with the Prandtl-Glauert correction for compressible regime. Based on these computations, the compressible Navier-Stokes equations are numerically solved, yielding the velocity and pressure fields. ALM lift results are validated against unsteady aerodynamic theory in the subsonic regime. Moreover, results demonstrate an acoustic field consistent with a dipole distribution and a spectrum exhibiting a frequency corresponding to the plunging motion. Furthermore, the acoustic results are validated through an acoustic analogy approach, involving the prediction of the acoustic field via Green’s function. The prediction of the acoustic far-field using ALM is expected to significantly reduce the computational cost of compressible simulations applied to propeller and wind turbine aeroacoustics.

© 2025 Elsevier Masson SASA simplified integrated model of the flight dynamics of flexible aircraft is developed using the Rayleigh-Ritz and quasi-steady vortex-lattice methods. In a novel approach, the Rayleigh-Ritz method is applied to all structural components with the inclusion of six rigid-body shape functions per component, allowing the enforcement of compatibility conditions between components and the calculation of modes of vibration for the entire aircraft at once. Another novelty is that, although aerodynamic influence coefficient matrices are calculated only for the jig shape, the vortex-lattice method boundary conditions and force equations are implemented in vector form and updated throughout flight simulations, allowing the formulation to capture important nonlinear aerodynamic effects related, e.g., to angular velocities, follower forces due to wing dihedral deformation, and induced drag. The equations of motion consider mean axes and a set of unrestrained modes of vibration. For simplicity, beam-like components with small deformations are considered. Using quasi-steady aerodynamics avoids the greater unsteady aerodynamic model preparation effort and computational cost. These characteristics make the proposed integrated model potentially useful in the initial stages of aircraft design when unifying aeroelasticity and flight dynamics is mandatory, as is the case for next-generation commercial aircraft. Convergence in the Rayleigh-Ritz method is achieved by varying the number of shape functions and its application to an aircraft comprising 20 beams shows that, compared to a model with 3006 degrees of freedom, one with only 606 results in frequency errors of less than 4% for all modes below 25 Hertz. Applying the framework to aircraft with decreasing stiffness levels reveals important phenomena, such as reduced short-period mode damping and frequency, increased damping of wing bending aeroelastic modes, and increased susceptibility to aileron roll control reversal.

© 2025, American Institute of Aeronautics and Astronautics, Inc. All rights reserved.This paper explores control alternatives for a generic fighter jet focusing on handling qualities enhancement in the transonic flight regime. The aerodynamic coefficients of the aircraft exhibit abrupt variations due to shock wave interference, so nonlinear control strategies are suggested. MATLAB simulations are employed to analyze the influence of these control laws on aircraft dynamics, including automated routines for equilibrium calculations, linearization, and the design of a conventional gain-scheduled Stability Augmentation System (SAS). Preliminary results demonstrate the SAS’s lack of effectiveness in mitigating transonic nonlinearities when sensor measurement errors occur. Therefore, the application of two nonlinear control techniques is proposed and investigated: Nonlinear Dynamic Inversion (NDI) and an output based Incremental Nonlinear Dynamic Inversion (INDI). The controlled variable of the flight control system is selected based on analysis of the Zero Dynamics Matrix calculated for load factor at the pilot’s station, the C-star parameter, and a combination of C-star, true airspeed, and altitude. Whereas NDI and INDI techniques result in adequate performance and stability characteristics in nominal conditions, the INDI controller is confirmed to be more robust to sensor measurement errors.

© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.This study presents the fabrication and optimization of ultrathin silver (Ag) films by low-power DC magnetron sputtering for surface-enhanced Raman spectroscopy (SERS) applications, with emphasis on the synergistic roles of electromagnetic (EM) and chemical enhancement (CE) mechanisms. Ag nanostructures were deposited onto glass substrates with controlled deposition durations (10–300 s), enabling the formation of tunable morphologies ranging from isolated nanoparticles to quasi-continuous nanostructured films. Structural and optical analyses revealed that an ~ 8.2 nm-thick Ag film exhibits optimal SERS performance due to its interconnected architecture, high surface asymmetry, and enhanced plasmonic coupling. SERS measurements were conducted using two cationic dyes—Rhodamine 6G (R6G) and Rhodamine B (RhB)—selected for their well-characterized Raman signatures and distinct surface adsorption behaviors. The optimized Ag substrate achieved enhancement factors in the range of 10⁶–10⁹ and detection limits down to 7 × 10⁻12M. Wavelength-dependent experiments using 532 nm and 633 nm excitation revealed strong SERS responses at both wavelengths, with maximal enhancement observed at 633 nm due to superior resonance alignment with the localized surface plasmon modes of the film. Electromagnetic field estimations based on UV–Vis absorbance correlated well with experimental trends, confirming EM as the dominant mechanism. Nonetheless, energy-level alignment between the Ag Fermi level and the molecular orbitals of the dyes, particularly for R6G, supports a secondary contribution from CE, driven by charge-transfer interactions and electrostatic adsorption. These findings demonstrate that the concurrent optimization of nanostructure, plasmonic response, and analyte–surface interaction is essential for enhancing both EM and CE effects. The substrate also enabled detection of Escherichia coli, underscoring its potential for biosensing at ultra-trace levels.

© 2025 Elsevier LtdThis study investigates the influence of thickness on the structure and morphology of sputtered wurtzite GaN thin films and evaluates their potential as piezoelectric materials for surface acoustic wave (SAW) devices. High-quality GaN films were deposited on Si(100) and glass substrates via reactive magnetron sputtering under optimized conditions. X-ray diffractometry (XRD), Raman spectroscopy, and transmission electron microscopy (TEM) analysis confirmed a preferential c-axis orientation. A detailed assessment of the crystalline quality and structural properties revealed that films grown for 6 h on Si substrates exhibited superior crystallinity and lower defect density. However, increasing film thickness led to higher surface roughness, which may impact SAW device performance. These findings highlight the viability of sputtered GaN films for SAW applications, provided that deposition parameters are carefully controlled to balance crystallinity and surface roughness. This work demonstrates the potential of cost-effective sputtering technique for producing GaN films suitable for high-frequency SAW devices.

© 2025 The Authors. Published by American Chemical SocietyAtomic layer deposition (ALD) enables simultaneous passivation of silver and nanometer-scale tuning of the near-field landscape that controls surface-enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF). Here, sputtered ∼16 nm Ag films were conformally coated with 1–20 ALD cycles of Al2O3(≈0.17–1.76 nm) and analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), spectroscopic ellipsometry, UV–Vis spectroscopy, time-resolved fluorescence, large-area Raman mapping of Rhodamine 6G and finite-difference time-domain (FDTD) modeling. Morphology evolves from isolated oxide nuclei after one cycle through a conformal roughness-amplifying shell at 5–15 cycles to vertically elongated outgrowths at 20 cycles; ellipsometry confirms self-limiting growth with 0.10 ± 0.02 nm cycle–1. Optical measurements reveal three thickness regimes: ≤1 cycle (<0.2 nm) yields SERS-dominated behavior with picosecond quenching and intense Raman hotspots; ∼5 cycles (∼0.5 nm) provides the hybrid optimum, giving the highest Raman enhancement (EF ≈ 2 × 103) together with a 4-fold fluorescence-lifetime extension (⟨τ⟩ ≈ 26 ns) that signals strong MEF; whereas >10 cycles (>1 nm) attenuate both SERS and MEF as the evanescent field decays. FDTD maps based on AFM topographies reproduce the heavy-tailed hotspot distribution and identify the 0.5–1.0 nm window as the sweet spot for co-optimizing field confinement and radiative efficiency. Stability tests show that five-cycle coatings endure solvent rinsing and cotton-swab abrasion while retaining─or even increasing─SERS activity, whereas thicker oxides guarantee mechanical integrity at the cost of weaker near-fields. These combined results show an experimentally validated framework for engineering reusable, dual-mode plasmonic substrates by angstrom-level control of dielectric spacer thickness.

© 2024 by the authors.This study investigates the high-pressure structural and vibrational properties of nano-Sc2O3 using a combination of X-ray diffraction, Raman spectroscopy, and theoretical calculations. Nano-Sc2O3 maintains its cubic bixbyite structure up to 26.4 GPa, without evidence of phase transitions, contrasting with bulk Sc2O3, which transitions to a monoclinic phase around 25–28 GPa. Raman spectroscopy reveals a pressure-induced blue shift in the vibrational modes, indicating lattice compression, and the absence of new modes confirms the retention of the cubic symmetry. Theoretical predictions using density functional theory (DFT) closely match the experimental data, validating the computational approach we use to model the pressure-dependent vibrational behavior of nano-Sc2O3. Comparisons with previous studies seem to show that the nanoscale material exhibits enhanced structural stability compared to its bulk counterpart, likely due to size effects and surface energy contributions. These findings provide new insights into the behavior of nanomaterials under extreme conditions and highlight the potential applications of nano-Sc2O3 in high-pressure environments.

© 2025 The AuthorsThe present work performs a review for using hydrogen in aircraft propulsion systems analyzing challenges and opportunities with the two main driveline architectures: direct combustion of hydrogen and fuel cells. First, the capability of hydrogen aircraft to become more energy efficient than conventional aircraft are discussed on system level, by extending previous review work. Then, challenges for hydrogen combustion and ways to limit emissions by lean direct injection and micromix combustion are discussed. Polymer electrolyte membrane (PEM) and solid oxide fuel cells are reviewed and the outlook for high temperature PEM fuel cells and challenges with per- and polyfluoroalkyl substances (PFAS) emissions are discussed. Dual fuel aircraft and flexible combustion are discussed as ways to provide a transition to a hydrogen economy. Additionally, hybrid configurations and new cycles that simplify hydrogen integration are reviewed. Finally, recent promising results on water emissions and contrail formation for hydrogen combusting aircraft are discussed.

© 2025 by the authors.Adverse pressure gradients are intrinsic to compressor flow behavior and are further intensified by secondary effects associated with rotor tip clearance flow interactions. Tip clearance generates leakage flow, which leads to the formation of tip leakage vortices, a major contributor to aerodynamic losses in axial compressors. These vortices significantly influence both compressor performance and operational stability. Extensive prior research has demonstrated that passive casing treatments, particularly axial slots, can substantially improve the stall margin in axial compressors. In this work, the performance of a new casing treatment geometry is investigated using the concept of recirculating flow within semi-circular axial slots. The proposed casing treatment geometry builds upon recent experimental findings involving single-rotor configurations. It was applied to the first rotor row of a three-and-a-half-stage (3.5-stage) axial compressor comprising an inlet guide vane followed by three rotor–stator stages. The numerical model incorporates axial slots with a novel periodic interface approach implemented in a multistage compressor simulation. Three-dimensional steady-state RANS (Reynolds Average Navier-Stokes) simulations were performed to investigate the aerodynamic effects of the casing treatment across various rotational speeds. The results for the casing treatment configuration were compared with those of a baseline smooth casing. The introduction of the new casing treatment produced noticeable modifications to the internal flow structure, particularly in the tip region, resulting in improved overall compressor stability within the operating range of 85 to 100% of design speed.

© 2025 by the authors.Turbines are rotating machines that generate power by the expansion of a fluid; due to their characteristics, these turbomachines are widely applied in aerospace propulsion systems. Due to the clearance between the rotor blade tip and casing, there is a leakage flow from the blade pressure to the suction sides, which generates energy loss. There are different strategies that can be applied to avoid part of this loss; one of them is the application of so-called desensitization techniques. The application of these techniques on gas turbines has been widely evaluated; however, there is a lack of analyses of hydraulic turbines. This study is a continuation of earlier analyses conducted during the first stage of the hydraulic axial turbine used in the low-pressure oxidizer turbopump (LPOTP) of the space shuttle main engine (SSME). The previous work analyzed the application of squealer geometries at the rotor tip. In the present paper, winglet geometry techniques are investigated based on three-dimensional flowfield calculations. The commercial CFX v.19.2 and ICEM v.19.2 software were used, respectively, on the numerical simulations and computational mesh generation. Experimental results published by the National Aeronautics and Space Administration (NASA) and data from previous works were used on the computational model validation. The parametric analysis was conducted by varying the thickness and width of the winglet. The results obtained show that by increasing the winglet thickness, the stage efficiency is also increased. However, the geometric dimension of its width has minimal impact on this result. An average efficiency increase of 2.0% was observed across the entire turbine operational range. In the case of the squealer, for the design point, the maximum efficiency improvement was 1.62%, compared to the current improvement of 2.23% using the winglet desensitization technique. It was found that the proposed geometries application also changes the cavitation occurrence along the stage, which is a relevant result, since it can impact the turbine life cycle.

Copyright © 2025 by ASME.Due to the growing relevance of mitigating climate change, and the race to improve the energy efficiency of aircrafts, aiming a goal of net-zero emissions of CO2 by 2050, the aircraft propellers have been receiving more attention, as they could represent the next innovation towards the efficiency improvements, especially due to the possibility of hybrid/electrical propulsion. In this context, this article consists of a critical overview of propeller design methods, depicting some relevant classical methods of designing propellers, such as the Blade Element Momentum Theory by Glauert, Vortex Theories, developed by Betz, Goldstein, and Theodorsen, as well as methods to design propellers that are intended to increase the lift on the wings. The straightforward Propeller Design procedures by Larrabee, Adkins Liebeck, and Wald, which are based on these theories, are also covered and compared. In addition, this paper also covers the final design and optimization, showing how computational methods, such as VLM and CFD, are being used in the literature to improve preliminary designs and model the interaction between the propellers and the wing/body. The objective of this paper is to provide a comprehensive reference for researchers and students, summarizing the state-of-Art of propeller design and optimization, for those who intend to work with propellers for green aviation.

© The Author(s), under exclusive licence to Springer Nature B.V. 2024.This paper is concerned with the robust position and attitude control of fully actuated fixed-wing multirotor aerial vehicles in the presence of disturbances and model uncertainties. To address this problem, we formulate the system using the vehicle’s nonlinear equations of motion considering the aerodynamic effects of the fixed wing as an additional disturbance. Then, we propose disturbance-observer-based attitude and position control laws using hybrid prescribed-time algorithms to control the vehicle and estimate model uncertainties and disturbances in two stages. In the first stage, the aforementioned algorithms employ nonautonomous formulations to ensure the convergence of the tracking and estimation errors to the origin in a prescribed time interval. Subsequently, in the second stage, the algorithms assume autonomous formulations to ensure robust stability of the errors over the infinite time domain. The proposed method is numerically evaluated, showing to be effective in providing the prescribed-time convergence of the tracking errors to zero and keeping them there afterwards.

© 2024 John Wiley & Sons Ltd.This paper is concerned with the prescribed-time robust attitude determination (AD) of multirotor aerial vehicles (MAVs) using vector measurements from the local magnetic field and local gravity. To address this problem, we first introduce a novel modified super-twisting algorithm endowed with the prescribed-time convergence property. The (Formula presented.) state of the proposed algorithm is governed by an unbounded time-varying gain up to the prescribed settling time (PST) and by a (Formula presented.) function after that. Therefore, after the PST, the new algorithm coincides with the conventional super-twisting, thus showing robust stability at the origin. This prescribed-time super-twisting algorithm (PTSTA) is then applied to the formulation of a three-stage gyro-free attitude determination method for MAVs. In the first stage, the classical QUEST algorithm is used to compute a Wahba-optimal attitude estimate from the vector measurements. In the second stage, the PTSTA is employed in the formulation of a robust state estimator that provides estimates of the attitude Gibbs vector and its rate. Finally, in the third stage, these state estimates as well as the attitude kinematic equation are immediately used to compute the MAV angular velocity. The proposed robust prescribed-time gyro-free AD method is evaluated numerically, showing invariance with respect to disturbance and model uncertainty.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.This chapter explores advancements in achieving stability within prescribed convergence time constraints. Drawing from the evolution of stability concepts, including finite-time stability (FTS), fixed-time stability (FxTS), and predefined-time stability (PTS), the chapter presents strategies to address the limitations of traditional FTS methods. Furthermore, it introduces a novel two-stage super-twisting algorithm (STA) that ensures robust prescribed-time state convergence by employing both time-varying and switching gains. By tuning these gains, we guarantee that the proposed algorithm’s analytic solution robustly reaches the origin exactly at the prescribed time. Numerical simulations involving a state-observer-based control problem for a perturbed damped pendulum validate its performance. The results show that the estimation errors converge robustly to the origin at the prescribed instants and remain there afterward. Moreover, a second-order sliding mode is obtained for the controller, driving the tracking errors asymptotically to the origin.

© 2025 Elsevier LtdVibration attenuation based on viscoelastic dampers have long been used to cope with a variety of industrial problems. Nonetheless, the quest for improving the effectiveness of those dampers is still an active research topic. Very often, technical and economical constraints involved in traditional manufacturing processes of more complex damping devices must be dealt with. The emergence and development of additive manufacturing technology have opened promising opportunities for innovative solutions. Among the existing technologies, PolyJetTM is an additive manufacturing technique in which an object is built in successive layers by jetting drops of ultraviolet curable liquid photopolymers, thus enabling to create complex, non-homogenous parts, with high geometric accuracy and finishing quality. This paper intends to fulfil some research needs by reporting investigations conducted to assess the damping performance of a novel design of viscoelastic surface treatment, named herein “lamellar damper”, which offers the possibility of achieving vibration mitigation goals by setting the design parameters. The research work involves both numerical modelling and experimental testing. For the later, PolyJetTM is used to manufacture prototypes of the lamellar damper. Confined to beam-like structures, the study comprises: 1) the development of low- and high-fidelity finite element models intended to predict the damping levels provided by the dampers considered, in comparison with conventional constrained layer dampers; 2) the realization of vibration tests on a beam to which 3D-printed lamellar dampers are applied, aiming at obtaining a set of frequency response functions and quantifying the associated natural frequencies and modal damping ratios. In addition, simulations are performed to assess the influence of relevant design parameters on the damping performance of lamellar dampers. The conclusions of the investigation indicate that the lamellar damper can provide improved damping performance and that PolyJetTM can be a viable and efficient process for the manufacturing of those dampers for practical applications.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.This paper approach the frontiers of autonomous space robots powered by an onboard computer containing artificial intelligence algorithms. Autonomous space robot systems are designed for performing tasks in space, such as on-orbit servicing, space assembly of large space structures, vehicle modules replacing, satellite orbit elevation/decay, cleaning orbit to prevent collisions with space debris, autonomous rendezvous docking/berthing as well as tasks for planetary exploration missions. Space robot manipulator type spacecraft or manipulator mounted on a space structure are capable of performing various tasks, such as grasping objects, manipulating tools, or interacting with the environment. Its capability extends from orbit environment to surface of planets, their moons and other celestial bodies as comets and asteroids. The frontier of the space robotics development, mainly those for planetary explorations relies in designing them to perform tasks autonomously. The term “autonomous” refers to the ability of the robot manipulator system to operate and make decisions without direct human intervention. Due to the long time delay to receive signal at planetary distances, autonomous robots are critical for effectively operates in Mars. Autonomous ability relies on onboard sensors, artificial intelligence algorithms, and control mechanisms. A branch of artificial intelligence, computer vision, plays a crucial role in autonomous space robot systems by enabling them to perceive and understand their environment, identify object patterns, and make informed decisions. Automatic manipulator operating nowadays differs from the near future autonomous robotic systems. While the automatic robots typically follow pre-programmed instructions or commands to perform a specific set of actions, an autonomous robot system powered by onboard computer vision possesses decision-making capabilities and can dynamically respond to its environment, allowing for greater flexibility and autonomy in its operations. The field continues to evolve, and researchers are exploring new architectures, techniques, and applications to advance computer vision systems capabilities.

© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.This study presents the fabrication and optimization of ultrathin silver (Ag) films by low-power DC magnetron sputtering for surface-enhanced Raman spectroscopy (SERS) applications, with emphasis on the synergistic roles of electromagnetic (EM) and chemical enhancement (CE) mechanisms. Ag nanostructures were deposited onto glass substrates with controlled deposition durations (10–300 s), enabling the formation of tunable morphologies ranging from isolated nanoparticles to quasi-continuous nanostructured films. Structural and optical analyses revealed that an ~ 8.2 nm-thick Ag film exhibits optimal SERS performance due to its interconnected architecture, high surface asymmetry, and enhanced plasmonic coupling. SERS measurements were conducted using two cationic dyes—Rhodamine 6G (R6G) and Rhodamine B (RhB)—selected for their well-characterized Raman signatures and distinct surface adsorption behaviors. The optimized Ag substrate achieved enhancement factors in the range of 10⁶–10⁹ and detection limits down to 7 × 10⁻12M. Wavelength-dependent experiments using 532 nm and 633 nm excitation revealed strong SERS responses at both wavelengths, with maximal enhancement observed at 633 nm due to superior resonance alignment with the localized surface plasmon modes of the film. Electromagnetic field estimations based on UV–Vis absorbance correlated well with experimental trends, confirming EM as the dominant mechanism. Nonetheless, energy-level alignment between the Ag Fermi level and the molecular orbitals of the dyes, particularly for R6G, supports a secondary contribution from CE, driven by charge-transfer interactions and electrostatic adsorption. These findings demonstrate that the concurrent optimization of nanostructure, plasmonic response, and analyte–surface interaction is essential for enhancing both EM and CE effects. The substrate also enabled detection of Escherichia coli, underscoring its potential for biosensing at ultra-trace levels.

© 2025 Elsevier LtdThis study investigates the influence of thickness on the structure and morphology of sputtered wurtzite GaN thin films and evaluates their potential as piezoelectric materials for surface acoustic wave (SAW) devices. High-quality GaN films were deposited on Si(100) and glass substrates via reactive magnetron sputtering under optimized conditions. X-ray diffractometry (XRD), Raman spectroscopy, and transmission electron microscopy (TEM) analysis confirmed a preferential c-axis orientation. A detailed assessment of the crystalline quality and structural properties revealed that films grown for 6 h on Si substrates exhibited superior crystallinity and lower defect density. However, increasing film thickness led to higher surface roughness, which may impact SAW device performance. These findings highlight the viability of sputtered GaN films for SAW applications, provided that deposition parameters are carefully controlled to balance crystallinity and surface roughness. This work demonstrates the potential of cost-effective sputtering technique for producing GaN films suitable for high-frequency SAW devices.

© 2025 by the authors.Featured Application: This study demonstrates the potential of plasma-activated water (PAW) as a tunable oxidative medium for the controlled surface modification of hair fibers. By adjusting the reactive species profile through distinct plasma systems, PAW formulations can be optimized to preserve hair structure while inducing specific molecular changes, offering a foundation for the development of low-impact, plasma-based technologies in cosmetic hair treatment. Plasma-activated water (PAW), enriched with reactive oxygen and nitrogen species (RONS), presents oxidative and antimicrobial characteristics with potential in cosmetic applications. This study examined the effects of two PAW formulations—nitrate-rich (PAW-N) and peroxide-rich (PAW-P)—on human hair types classified as straight (Type 1), wavy (Type 2), and coily/kinky (Type 4). The impact of PAW on hair structure and chemistry was evaluated using Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), UV–Vis spectrophotometry, and physicochemical analyses of the liquids (pH, ORP, conductivity, and TDS). PAW-N, with high nitrate content (~500 mg/L), low pH (2.15), and elevated conductivity (6244 µS/cm), induced significant damage to porous hair types, including disulfide bond cleavage, protein oxidation, and lipid degradation, as indicated by FTIR and EDS data. SEM confirmed severe cuticle disruption. In contrast, PAW-P, containing >25 mg/L of hydrogen peroxide and exhibiting milder acidity and lower ionic strength, caused more localized and controlled oxidation with minimal morphological damage. Straight hair showed greater resistance to both treatments, while coily and wavy hair were more susceptible, particularly to PAW-N. These findings suggest that the formulation and ionic profile of PAW should be matched to hair porosity for safe oxidative treatments, supporting the use of PAW-P as a gentler alternative in hair care technologies.

© 2025 Elsevier LtdThe innovative concept of thermite Plugging and Abandonment (thermite P&A) is designed to enhance cost-effectiveness and reliability in the permanent sealing of oil wells. This technique relies on a controlled exothermic reaction between aluminum powder (Al) and iron (III) oxide (Fe2O3), generating sufficient heat to trigger phase change phenomena and melt structural components of the borehole. However, the associated thermal interactions remain insufficiently investigated. The present study is focused on predicting the heat conduction and phase change phenomena within a multi-layered cylindrical domain through analytical and numerical methods. Initially, the Distributed Transfer Function Method (DTFM) was applied to a one-dimensional radial analysis. The study was then extended to two-dimensional axisymmetric simulations using the Finite Volume Method (FVM), incorporating heat conduction, phase change, molten metal flow, and gravity effects. The enthalpy method, with a mushy zone approach, was used to compute liquid fractions, and the molten steel velocity field revealed convection effects, with a peak velocity of ∼ 1.8 cm/s. Temperature results showed that, while the cement acted as a thermal barrier preserving the cap rock, it experienced temperatures above 300 °C, risking structural damage. The findings offer valuable insights into thermite P&A and highlight the robustness of analytical frameworks in modern engineering applications.

© 2025A hybrid analytical framework based on the Distributed Transfer Function Method (DTFM) is presented for solving the one-dimensional transient heat conduction problem in multilayer wall systems. A novel adaptive step-wise segmentation strategy is introduced to extend the applicability of DTFM to non-differentiable boundary conditions—specifically, measured solar heat flux and ambient air temperature data recorded during the summer in Gaziantep, Turkey. These experimental signals were modeled using Gaussian and sinusoidal regression schemes and segmented into analytically tractable intervals to ensure continuity and differentiability within the DTFM solution domain. Six wall configurations were evaluated under convective–radiative boundary conditions, with the interior air temperature maintained at 25 °C. The resulting transient heat flux at the inner surface was interpreted as the instantaneous Heating, Ventilation and Air Conditioning (HVAC) thermal load and integrated over time to compute the daily cooling and heating energy demands. Among all cases, the five-layer wall with EPS insulation (W6) yielded the lowest AC energy consumption at 0.343 kWh, while the three-layer brick wall (W1) reached 1.165 kWh—representing a 70.5 % reduction. Comparative analysis also identified near-equivalent thermal responses in W2 – Autoclaved Aerated Concrete (AAC) vs. W3 (blockbim) and W1 (brick) vs. W4 (briquette), with subtle yet quantifiable differences in energy performance. The DTFM predictions were benchmarked against Finite Volume Method (FVM) simulations, showing temperature deviations below 1 °C. The method's capacity to incorporate segmented regressions, solve eigenvalue problems, and construct modal solutions across complex wall geometries makes it a robust and efficient tool for transient thermal analysis. The proposed framework enables high-fidelity assessment of building envelope performance under time-varying environmental conditions, providing valuable insights for HVAC optimization and passive design strategies.

© 2025 Elsevier LtdFor the petroleum industry, one of the most critical and expensive stages of offshore platform decommissioning is the wellbore plugging and abandonment (P&A) operation. Decommissioning standards require that, at the end of its lifespan, the wellbore be permanently sealed to impede the spill of contaminating hydrocarbons into marine ecosystems or aquifers. The current decommissioning operation comprises removing the production tubing, machining the borehole casing, and cementing the machined section to seal the wellbore. Such an operation has a relatively high cost and several risks. An alternative technology is replacing cement with a metallic plug created by the thermite reaction. This technology still needs improvements to be successfully employed in offshore oil fields, and numerical simulation is a useful tool to optimize critical parameters. We developed an axisymmetric, finite-element-based heat conduction model to simulate the thermite reaction and the temperature evolution inside a typical wellbore. The phase change of both thermite and wellbore components is calculated using the apparent heat capacity method, and a moving mesh scheme is proposed to capture the reaction fronts. We perform numerical simulations to verify and validate the model, and we run different P&A scenarios while discussing risks and opportunities for this new technology.

© 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Additively manufactured components often exhibit microstructural heterogeneity, leading to anisotropy. Most works are dedicated to a specific feature, and a full characterization has not been addressed yet. This study characterizes these heterogeneities in a carbon steel part made by wire arc additive manufacturing (WAAM) and correlate them numerically with physical phenomena A deep microstructural, mechanical, and surface analysis was carried out for three main regions of the wall: top, middle and bottom. The cooling rate and the number of subsequent passes are the main factors influencing microstructure variation on the layers, steady-state regime was reached at layer 30. Electron backscatter diffraction (EBSD) analysis showed uniform grain orientation and similar size, with ferrite increasing from the top to the bottom, while the amount of retained austenite and cementite, decreased. The top region showed diverse microconstituents due to the absence of reheating cycles in the last layers. Microhardness values varied with average of 223.3, 176.3 and 187.6 HV0.1 for top, middle and bottom regions, respectively, the same trend was found in the simulation. Tensile tests indicated minor anisotropy in yield strength (YS) and ultimate tensile strength (UTS), but significant anisotropy in elongation. The anisotropic percentages of YS, UTS, and elongation come to 0.9 %, 0.4 %, and 10.9 %, respectively. Scanning electron microscopy (SEM) analysis presented ductile failure in both vertical and horizontal orientations. Surface characterization indicated similar topography on both sides of the wall. Overall, it exhibited homogeneous microstructural characteristics and surface topography, but heterogeneous mechanical properties, particularly in elongation.

© 2025 by the authors.Featured Application: This research directly contributes to designing more sustainable and efficient milling processes within the mineral processing industry. It provides a detailed guide for converting ball mills from conventional overflow systems to more energy-efficient grate discharge systems by optimizing breakage rates and material transport. These enhancements deliver substantial benefits, such as increased throughput, reduced power consumption, and steeper particle size distribution. This study examines the conversion of an overflow ball mill into a new discharge system via Discrete Element Method (DEM) and Smoothed Particle Hydrodynamics (SPH) simulations, demonstrating significant performance improvements. The methodology integrates SPH to assess the effects of the slurry on energy dissipation, power loss, breakage rates, and material transport. The findings highlight significant operational inefficiencies in the overflow setup, extensive dead zones, and excessive charge volume that hinder milling efficiency by limiting grinding media interaction with the ore and reducing energy for comminution. Additionally, slurry pooling shifts the center of gravity, causing torque losses and direct material bypass to the discharge zone. Our simulations replicate these challenges and benchmark them against industrial-scale operations, identifying critical charge excesses that constrain throughput and elevate power consumption. The new proposed discharge system decouples the filling charge from the evacuation mechanism, releasing the effective volume in the mill, in addition to tackling common issues in the traditional grate discharge setups like backflow and carry-over. This arrangement substantially improved grinding efficiency, as demonstrated by enhanced breakage rates and diminished specific energy consumption. The results provide a robust framework for mill design and operational optimization, underscoring the value of integrated slurry behavior analysis in mill performance enhancement.

© 2024 Elsevier LtdThe thermal characterization of materials at high temperatures is crucial to various modern engineering applications. However, direct experimental measurements under severe conditions can be complex, expensive and offer several other disadvantages. Hence, in this work, a novel Radial Basis Function (RBF) based inverse method is proposed as an alternative to solve nonlinear Inverse Heat Transfer Problems (IHTPs). Here, a proof of concept is performed by estimating a two parameters exponential function describing the specific heat of an AISI 1020 steel submitted to LASER Beam Welding (LBW). An inverse algorithm combined with an RBF interpolation algorithm enables an enhanced search domain scan. A least squares objective function with Future Time Regularization (FTR) is implemented to govern the estimation. The algorithms are sequentially run and refeed to refine the minimization region through adjustable search factors. A Finite Volume Method (FVM) thermal model was implemented through a highly parallelized inhouse CUDA-C code, run on an Nvidia Geforce® RTX™ 3090. A verification was performed using three commercial solutions. The method's efficiency was demonstrated with both noiseless and variable standard deviation data. The approach is less sensitive to local minima than previous Quadrilateral Optimization Method (QOM), with estimation errors below 1.0 % in nearly all cases.

© 2025, Begell House Inc. All rights reserved.This study presents an in-depth comparative analysis with a widely used turbulence model in Computational Fluid Dynamics (CFD): the standard k-ε model. The research focuses on turbulent flow over a backward-facing step (BFS), a classical problem known for its complex recirculation and reattachment phenomena. Simulations were conducted using both an innovative Graphics Processing Unit (GPU) based parallel processing algorithm developed on the Nvidia Compute Unified Device Architecture (CUDA) platform, and a Central Processing Unit (CPU) based commercial software. The numerical simulation analysis spans a broad range of Reynolds numbers, representing different levels of turbulence intensity, and compares the performance of these two approaches. The primary objective of this study is to evaluate the predictive capabilities of the standard k-ε model in terms of reattachment length, a critical parameter for accurately capturing the dynamics of separated flows. The simulation results obtained from both software platforms are rigorously compared with classical experimental data at ReH = 36,000 to assess the accuracy and reliability of each approach. The GPU simulations were performed on an Nvidia GeForce RTX™ 3090Ti with 24 GB of video memory, while the commercial simulations were run on an Intel®Core™ i7-12700H CPU, featuring a 2.3 GHz base clock and 14 cores. The results indicate that GPUs offer a more optimal architecture for CFD problem-solving, leveraging large-scale computational parallelization.

© 2025, Begell House Inc.. All rights reserved.This study presents a numerical investigation of Von Karm an flow at a Reynolds number of 200, induced byflow past a single cylinder. The Von Karm an vortex street, characterized by alternating vortices shed froma bluff body, is a fundamental phenomenon in fluid dynamics with significant applications in engineering systems. We employ the Finite Volume Method (FVM) to discretize the governing Navier-Stokes equations, capturing the intricate interactions within the velocity field surrounding the cylinder. Computations are performed using Graphics Processing Units (GPUs) to leverage their parallel processing capabilities. The GPUaccelerated FVM achieves a computational speedup of 50 times compared to traditional calculations on an Intel i9 CPU. This substantial acceleration enables high-resolution simulations that provide deeper insights into the flow structures of the system. The results demonstrate the effectiveness of GPU computing in solving complex fluid dynamics problems and highlight its potential to advance research in computational fluid dynamics.

© 2025, Begell House Inc.. All rights reserved.This study presents an in-depth examination of a three-dimensional conjugate heat transfer (CHT) model within a cubic cavity containing a solid cubic insert, engineered to investigate the thermal interaction at the fluid-solid interface. The thermal gradient induced across the cavity’s walls initiates fluid motion via natural convection, effectively modeled using the Boussinesq approximation to address the fluid’s thermally induced density variations. Central to this research is the development of an innovative CHT approach that employs a coupled boundary condition, integrating the heat conduction equations of the solid and the thermal-fluid dynamics equations of the fluid into a seamless analytical framework. This integration not only facilitates a comprehensive analysis of the fluid-solid interface but also enhances the accuracy and coherence of the simulation results. By treating the solid and fluid components as interconnected systems through the coupled boundary condition, the study demonstrates significant improvements in the predictability of temperature distribution and flow patterns within the cavity. Validation against established benchmarks confirms the model’s superior capability in capturing complex interactions at the fluid-solid boundary, highlighting its potential to advance thermal management strategies across a variety of engineering applications. The paper underscores the efficiency and reliability of the new approach, showcasing its value in providing more detailed insights into the intricate dynamics of heat transfer and fluid movements, crucial for optimizing design processes in both academic research and industrial practice.

© The Author(s), 2024.This article presents a systematic review on the use of eye-tracking technology to assess the mental workload of unmanned aircraft system (UAS) operators. With the increasing use of unmanned aircraft in military and civilian operations, understanding the mental workload of these operators has become essential for ensuring mission effectiveness and safety. The review covered 26 studies that explored the application of eye-tracking to capture nuances of visual attention and assess cognitive load in real-time. Traditional methods such as self-assessment questionnaires, although useful, showed limitations in terms of accuracy and objectivity, highlighting the need for advanced approaches like eye-tracking. By analysing gaze patterns in simulated environments that reproduce real challenges, it was possible to identify moments of higher mental workload, areas of concentration and sources of distraction. The review also discussed strategies for managing mental workload, including adaptive design of human-machine interfaces. The analysis of the studies revealed a growing relevance and acceptance of eye-tracking as a diagnostic and analytical tool, offering guidelines for the development of interfaces and training that dynamically respond to the cognitive needs of operators. It was concluded that eye-tracking technology can significantly contribute to the optimisation of UAS operations, enhancing both the safety and efficiency of military and civilian missions.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.The development of assistive devices for the blind and visually impaired (BVI) has often overlooked the essential participation of BVI users in the design process, resulting in products that are not user-friendly for them. This paper introduces a virtual reality (VR)-based framework designed to integrate BVI users into the development of assistive technologies actively. Leveraging VR, the framework facilitates immersive and interactive product testing environments where BVI users can directly evaluate and provide feedback on assistive device prototypes. This method allows for real time adjustments and refinements, significantly enhancing the usability of the products. The setup integrates two scenarios, one virtual and one real, each built with identical configurations. As BVI users navigate the real scenario, their interactions inform the virtual scenario in real-time, allowing for immediate adjustments and refinements. This paper evaluates this framework and seeks to determine if human factors can be used to evaluate assistive products and if non-BVI users, when deprived of their vision, can similarly evaluate assistive devices as BVI users. The proposed framework seeks to elevate the practical utility of assistive devices and to include the users in the design process.

© 2025 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.This study presents a novel deep learning-based method for inspecting aerospace sealants, utilizing a modified Mask Region-Based Convolutional Neural Network (Mask RCNN) for defect detection and segmentation. Inspired by medical image analysis techniques, the methodology involves training the modified Mask RCNN model to detect and classify defects in aerospace sealants, such as bubbles, cracks, and irregular application patterns. Several images of sealant applied to various surfaces are used for training, with data augmentation techniques enhancing the dataset to ensure robust performance under diverse conditions. Once trained, the model automatically generates detailed reports that highlighting the professional roles involved. The proposed method aims to improve maintenance efficiency, reduce human error, and ensure the quality of aerospace sealants, ultimately contributing to the overall safety and performance of aerospace components.

© The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2024.This paper is dedicated to structure-preserving spatial discretization of shallow water dynamics. First, a port-Hamiltonian formulation is provided for the two-dimensional rotational shallow water equations with viscous damping. Both tangential and normal boundary port variables are introduced. Then, the corresponding weak form is derived and a partitioned finite element method is applied to obtain a finite-dimensional continuous-time port-Hamiltonian approximation. Four simulation scenarios are investigated to illustrate the approach and show its effectiveness.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The Professional Master Program in Aeronautical Engineering (MP-AER) is an initiative established in 2002 between ITA (Aeronautical Institute of Technology) and Embraer Industry to prepare new engineers for the development of new aircraft ventures. This Graduate Program has four phases. Phase 1 (first semester) offers courses in Fundamentals in Aeronautical Engineering. In Phase 2 (second semester) the student has to choose one career track and take several courses. In Phase 3 (third semester) all the students develop, in groups, the Capstone Aeronautical Project. In Phase 4, the student develops a Master’s Thesis. The purpose of this paper is to describe how the Capstone Project is organized and evaluated according to ABET criteria. The whole program description, the capstone project, and the continuous assessment and improvement processes are presented in detail. It is also shown how the Capstone Project prepares graduate students for a rapidly evolving work environment, which contributes to foster aeronautics in Brazil.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This paper introduces a newapproach to modal synthesis by integrating simulations with realscale experiments. The technique partitions the complete aircraft structure into substructures: one representing the aircraft itself and others representing the hanging substructure that connects to the wing. A method is presented for imposing new frequencies on the vibration modes of the hanging substructure. Subsequently, experimentally obtained frequencies for the clamped substructure’s roll, yaw, and pitch vibration modes are imposed to evaluate the benefits in accurately predicting the overall aircraft behavior. As a result, the predicted frequency for the roll vibration mode of the substructure in the aircraft increased from 7.6 Hz to 11.9 Hz, while the result from real-scale ground vibration test was 11.6 Hz.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This paper showcases the collaborative efforts between ITA (academic) and Embraer (aircraft manufacturer) in developing advanced methods to address the upcoming challenges of the 4th Aeroelastic Prediction Workshop. For predicting static wing loads, a rapid conceptual design method that accounts for structural geometric nonlinearity is introduced. A matched flutter solution is proposed for control surface flutter in geometrically nonlinear wings. For predicting limit cycle oscillations, the approach combining an unsteady vortex lattice with a transient structural geometric nonlinear solver is presented. Furthermore, a framework that integrates an open-source Reynolds-Averaged Navier-Stokes solver with a geometric nonlinear structural solver is developed to handle transonic static deflections.

© 2025 Elsevier B.V.This study explores the synthesis and comprehensive characterization of thick coatings developed using alumina (liquid phase) and zirconium silicate (solid phase) hybrid precursors. The coatings were deposited onto graphite substrates using a supersonic plasma spray process, allowing for the simultaneous deposition of liquid and solid phases, and forming Al₂O₃, SiO₂, ZrO₂, and ZrSiO₄. Advanced characterization techniques, including SEM, EDS, XRD, Raman spectroscopy, FTIR, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), were employed to investigate the microstructure, phase composition, and thermal stability of the coatings. The TGA/DSC results revealed critical thermal events, including the crystallization of spinel and α-Al₂O₃ phases, mullite formation, and ZrSiO₄ recrystallization, suggesting the hybrid precursor's effectiveness in generating thermally stable phases. Post-thermal testing at 1400 °C showed increased tetragonal ZrO₂ content and the formation of amorphous and aluminosilicate phases, convenient to enhanced coating densification, self-healing properties, and thermal resistance. These findings highlight the potential of hybrid precursor-based coatings for high-temperature applications, pointing toward the development of a robust solution for advanced thermal and environmental barrier systems in the aerospace and industrial sectors.

© 2025 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.This study investigates the thermal plasma pyrolysis process for inertizing the inorganic fraction of sewage sludge from municipal wastewater treatment plants. The aim is to assess its effectiveness in waste inertization. Lab-scale experiments were conducted to process the sludge thermally. Elemental composition analysis was done using x-ray fluorescence (XRF), thermogravimetry coupled with mass spectrometry (TGA-MS) and x-ray diffraction (XRD). The XRF analysis showed an initial composition of Si, Al, Fe, and Ca, corresponding to 86.8% of the inorganic matter of the sludge. TGA-MS analysis showed a significant mass loss between 200 and 650 ◦C, corresponding to organic matter volatilization, methane conversion, and dehydrogenation of polymorphic silicon. XRD analysis revealed a dried sludge crystalline structure composed mainly by SiO2, CaCO3, and AlPO4, and after plasma treatment, the remaining composition of the slag was primarily SiO2 amorphous. Mass and energy balances, considering thermodynamic equilibrium and chemical reactions, are performed. The mass balance calculations identified the most probable composition of the sludge, and energy balance calculations determined a net energy requirement of 399 kWh for plasma inertization, with an additional 300 kWh to account for furnace losses. Solubility and leaching tests confirm the inert nature of the residue. Power requirements are estimated at 700 kW for processing 350 kg h−1 of decarbonized sludge. These findings are crucial for optimizing plasma inertization processes in wastewater treatment plants. This work presents a novel approach by combining a computational prediction for an industrial-scale plant with a direct experimental assessment of the plasma treatment process.

© The Author(s), under exclusive licence to Springer Nature B.V. 2025.Silver nanoparticles (AgNPs) have been extensively studied due to their antimicrobial properties against several pathogenic microorganisms. A particularly promising application of these nanoparticles involves their incorporation into textiles to enhance the efficacy of face masks. This work aims to deposit AgNPs on polyamide 6,6 fabrics using a hybrid corona-dielectric barrier discharge plasma reactor and evaluate their antimicrobial effect as well as their cytotoxicity. Prior to deposition, the fabrics were activated in air plasma at atmospheric pressure. The deposition process was then initiated by nebulizing a silver nanoactive into the system by a flat cavity present in the high-voltage electrode, a distinctive feature that sets this approach apart from other AgNP deposition techniques reported in the literature. The incorporation of AgNPs on polyamide 6,6 fabric surface was confirmed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The thermal behavior of the samples was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). To identify the crystalline phases, X-ray diffraction (XRD) analyses were performed on control (without AgNPs) and treated (with AgNPs) samples. Microbiological analysis was based on the AATCC 100–2019 test method with modifications for two different species of bacteria: Staphylococcus aureus and Klebsiella pneumoniae. Bacterial suspensions with 1–3 × 105 cells/mL were inoculated into control and treated samples, followed by viable cell count (CFU/mL). Statistically significant reductions in bacterial counts were detected, with 62.37% and 74.63% reduction percentages compared to the control sample for Staphylococcus aureus and Klebsiella pneumoniae, respectively. Furthermore, cytotoxicity analysis, performed according to ISO 10993–5/2009, showed that the treated fabrics are not cytotoxic due to higher viability than 70%.

© 2025 The Author(s). Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals LLC.As life expectancy rises, the demand for effective bone regeneration materials becomes imperative, particularly in addressing age-related conditions such as osteoporosis, arthritis, and dental surgeries. This study focuses on the urgent development of materials aimed at filling the implant-bone interface and enhancing bone regeneration. Wollastonite (CaSiO3), a calcium silicate ceramic, stands out for its superior biocompatibility and hydroxyapatite-forming capability compared to phosphate-based cements. The primary objective of this research is to assess the influence of different wollastonite phases and buffered solutions on the production of calcium silicate cements. Four types of cement were evaluated, varying the studied phase (α and β-wollastonite) and the activating solution ((NH4)2HPO4 and K2HPO4). Characterization techniques such as X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and scanning electron microscopy (SEM) were employed to elucidate the impact of each phase and ion on material properties. Compressive strength analysis and biological tests were also conducted. The physicochemical analysis revealed that the α-wollastonite phase exhibits more non-bridge oxygen (NBO) bonds and silanol groups than β-wollastonite, suggesting superior bioactivity. XRD, FT-IR, and Raman results demonstrated that cements prepared with ammonium buffer solutions formed hydroxyapatite, enhancing compatibility with bone tissue. Compressive strength tests showed overall equivalent strengths (approximately 6 MPa), except for the sample prepared with β-wollastonite and potassium phosphate, which exhibited lower resistance to compression. Alkaline phosphatase data indicated that cements formed with α-wollastonite phase and (NH4)2HPO4 presented superior potential for bone regeneration.

© 2025 Elsevier Inc.Objective: To evaluate the fatigue life of 5Y-PSZ crowns coated with antimicrobial glasses and the wear on the antagonist, comparing it to a commercial glaze. Methods: Forty-five crowns of 5Y-PSZ zirconia were divided into: commercial glaze (G); boron-doped soda-lime glass (BSL), and boron-doped soda-lime glass with silver (BSLAg). Step-stress accelerated life testing was conducted at 2 Hz with a stress ratio of 0.1 on a custom servo-hydraulic load frame. The characteristic lifetime and Weibull modulus were estimated using the ALTAPRO software. Energy-Dispersive Spectroscopy (EDS), surface roughness (SR, Sa, and Sz) for the coated crowns and the pistons, fractography, and piston wear analysis were conducted. Crown's SR and piston wear were analyzed by two-way ANOVA, and Tukey's method (α=0.05). Piston's SR was examined by Linear Mixed Model (LMM) (α=0.05). Results: EDS identified zirconium in the composition of the radiopaque structures on both experimental glass coating surfaces. Crowns coated by BSL showed the lowest Sz values after all the different fatigue profiles. After the fatigue test, the SR (Sa and Sz) of the piston for all groups was similarly higher than before. No significant difference could be detected between the groups after the fatigue lifetime analysis. Fractures originated at the glass surface for all groups. The pistons in contact with the G group crowns presented greater volume wear for the mild fatigue profile. Significance: 5Y-PSZ zirconia crowns coated by BSL and BSLAg maintained the fatigue performance and significantly reduced wear on the piston/antagonist compared to the commercial glaze group. These coatings show potential for clinical applications in ceramic restorations, particularly in environments prone to biofilm accumulation.

© 2025 Elsevier Ltd and Techna Group S.r.l.This study investigated the effects of hydrothermal aging on the microstructural, optical, and mechanical properties of commercial and experimental 4Y-PSZ zirconia (4 mol% yttria-stabilized tetragonal zirconia polycrystal). Samples of commercial and experimental 4Y-PSZ were produced by milling CAD/CAM blocks and uniaxial pressing, respectively. Each group was characterized in three conditions: control, aged 20-h, and aged 50-h in a hydrothermal reactor. Density, microstructure, crystalline phase composition, optical, and mechanical properties were evaluated using Archimedes' principle, scanning-electron-microscopy (SEM), X-ray diffraction (XRD) with Rietveld refinement, reflectance tests, and biaxial-flexural-strength (BFS) tests, respectively. Data were analyzed using Weibull statistics and two-way ANOVA with Tukey's tests. Both groups achieved densification above 99%. Commercial zirconia displayed a homogeneous microstructure with smaller grains compared to experimental 4Y-PSZ. XRD patterns and Rietveld refinement revealed significant differences in phase composition between the groups in function of aging times. Initially, both groups presented high fractions of tetragonal and cubic phase, with no detectable monoclinic content. After 20 h of aging, a substantial increase in the monoclinic phase was detected in the experimental (39%) and commercial groups (29%). After 50 h, both groups reached approximately 40 % of monoclinic content, indicating transformation saturation. Aging affected optical properties in the experimental group but not in the commercial one. While the commercial group presented higher strength compared to the experimental group, a high survival probability was observed in both groups for missions up to 800 MPa. Extended hydrothermal aging led to strength reduction in the commercial group, while the experimental group remained stable. Significant differences in Weibull modulus were observed only in the commercial group between immediate and 50-h aged conditions. The study confirms the susceptibility of 4Y-PSZ zirconias to phase transformation but supports their suitability for long-span fixed dental prostheses, given their strength and reliability.

© 2025 The Author(s). Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals LLC.Skin injuries occur when cellular integrity is compromised due to mechanical, physical, or metabolic factors. This study reported on a carboxymethylcellulose (CMC)-based film incorporating TiNT, aiming at its application as a wound dressing. As a minimally invasive approach, titanate nanotubes (TiNT) have been studied due to their photocatalytic properties, biocompatibility, large pore volume, and high surface area. Functionalization with aminosilane groups, using the biological responses of nitrogen, has been explored to enhance cellular interaction. Upon exposure to UV radiation, the dressing releases nanotubes, protecting the lesion from external pathogens and promoting healing. TiNTs were synthesized via a hydrothermal method and 0.2% (v/v) functionalized using 3-aminopropyltrimethoxysilane (APTMS). The films were prepared with 1 (wt%) TiNT or TiNT_NH2 in a 2 (wt%) CMC solution and dried at 60°C for 24 h. Results showed enhanced thermal stability and the potential for controlled nanoparticle release under UV light, with no cytotoxic effects observed. The films demonstrated excellent biocompatibility, making them promising candidates for medical applications.

© 2025 The Author(s). International Wound Journal published by Medicalhelplines.com Inc and John Wiley & Sons Ltd.Chronic wounds may develop when there is a delay or disturbance in one of the stages of the healing process, presenting challenging financial, clinical, and quality-of-life costs. Therefore, continuous efforts have been made to develop dressings that optimise wound healing. In recent years, nanotechnology has revolutionised wound care, enabling the development of innovative materials with high efficiency that positively impact the healing process. Nanoparticles have been extensively used in wound dressings because of their specific properties, such as a high surface area-to-volume ratio, increased surface reactivity, and improved biocompatibility, representing a unique tissue repair tool. This review article addresses advances in the use of organic nanoparticles in the field of skin regeneration, considering papers published in the last 5 years, and highlighting the effects of this class of materials on the wound healing process. The analysis of the literature shows that the materials being considered are carbon-based and organic materials, including polymeric, cellulosic, lipid, and liposome nanoparticles, which are covered in this review (inorganic nanoparticles are not considered). Furthermore, important aspects to prevent the development of chronic wounds are presented, as well as general characteristics of wounds, the healing process, and their particularities.

© 2025 The AuthorsThe aim of this study was to synthesize an experimental bilayer zirconia composed of second-generation 3Y-TZP and ultra-translucent 4Y-PSZ, as well as to characterize its microstructure, optical, and mechanical properties, and compare it with its monolithic counterparts before and after hydrothermal aging. Disc-shaped specimens (ISO 6872:2015) were obtained by uniaxial pressing of commercial powders (Zpex and Zpex4; Tosoh Corporation). Then, the discs were sintered at 1550°C for 2 h and divided into 3 groups: bilayer 3Y/4Y, monolithic 3Y and 4Y. Half of the samples of each group were subjected to hydrothermal reactor aging (20 h, 2.2 bar and 134°C). Specimens were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. Optical properties were determined by contrast ratio (CR) and translucency parameter (TP). Mechanical properties were assessed by biaxial flexural strength. XRD evidenced 66 %, 32 %, 66 %, and 40 % of monoclinic phase for aged 3Y-bilayer, 4Y-bilayer, 3Y-control and 4Y-control, respectively. Raman spectra presented monoclinic content on the aged surface of 87 %, 45 %, 87 %, and 47 % for 3Y-bilayer, 4Y-bilayer, 3Y-control, and 4Y-control, respectively. SEM exhibited dense and homogeneous microstructure with smaller grains in bilayer groups, unaffected by aging. Hydrothermal aging did not influence TP and CR, regardless of the system. 3Y demonstrated lower TP and higher CR compared to 4Y and bilayer groups. Aging increased the characteristic strength of all groups. Fractographic marks indicated the origin of fracture and direction of crack propagation from tensile side defects to the compression surface. Hydrothermal aging triggered alterations in the crystalline content, microstructure, and mechanical properties of the experimental bilayer zirconia system as well as of their monolithic controls.

© 2025 Elsevier LtdThe aim of this study was to develop an experimental bilayer zirconia system composed of first-generation 3Y-TZP and super-translucent 4Y-PSZ, and to characterize its microstructural, optical, and mechanical properties before and after hydrothermal aging, comparing them with its monolithic controls. Disc specimens were produced through uniaxial pressing of commercial 3Y-SBE and ZPEX 4 powders (Tosoh Corporation) and sintered at 1550ºC for 2 hours. Hydrothermal aging was performed in a hydrothermal reactor for 20 hours at 134ºC and 2.2 bar. Microstructural characterization by scanning electron microscopy revealed smaller grains in the bilayer group compared to the control groups. X-ray diffraction indicated a lower susceptibility to hydrothermal degradation for the bilayer group, while Raman spectroscopy showed that degradation occurred only in the outermost layer. Optical characterization demonstrated that the bilayer system successfully combined the higher translucency of 4Y with the superior opacity of 3Y, resulting in an effective aesthetic balance between the layers. Mechanical evaluation indicated that the bilayer system remained stable before and after hydrothermal aging, with strength values exceeding 800 MPa. Fractographic analysis revealed that cracks originated on the tensile side and propagated towards the compressive side. It is concluded that the 3Y/4Y bilayer zirconia system presents a promising balance between aesthetics and strength, making it a viable solution for various dental applications.

© 2025 by the authors.Methylene blue (MB), a widely used industrial dye, is a persistent pollutant with documented toxicity to aquatic organisms and potential health risks to humans, even at ultra-trace levels. Conventional monitoring techniques such as UV–Vis spectroscopy and fluorescence emission suffer from limited sensitivity, typically failing to detect MB below ~10−7 M. In this study, we introduce a surface-enhanced Raman spectroscopy (SERS) platform based on silver nanowire (AgNW) substrates that enables MB detection over an unprecedented dynamic range—from 1.5 × 10−4 M down to 1.5 × 10−16 M. Raman mapping confirmed the presence of individual signal hot spots at the lowest concentration, consistent with the theoretical number of analyte molecules in the probed area, thereby demonstrating near-single-molecule detection capability. The calculated enhancement factors reached up to 1.90 × 1012, among the highest reported for SERS-based detection platforms. A semi-quantitative calibration curve was established spanning twelve orders of magnitude, and this platform was successfully applied to monitor MB degradation during two advanced oxidation processes (AOPs): TiO2 nanotube-mediated photocatalysis under UV irradiation and atmospheric-pressure dielectric barrier discharge (DBD) plasma treatment. While UV–Vis and fluorescence techniques rapidly lost sensitivity during the degradation process, the SERS platform continued to detect the characteristic MB Raman peak at ~1626 cm−1 throughout the entire treatment duration. These persistent SERS signals revealed the presence of residual MB or partially degraded aromatic intermediates that remained undetectable by conventional optical methods. The results underscore the ability of AgNW-based SERS to provide ultra-sensitive, molecular-level insights into pollutant transformation pathways, enabling time-resolved tracking of degradation kinetics and validating treatment efficiency. This work highlights the importance of integrating SERS with AOPs as a powerful complementary strategy for advanced environmental monitoring and water purification technologies. By delivering an ultra-sensitive, low-cost sensor (<USD 0.16 per test) and promoting reagent-free treatment methods, this study directly advances SDG 6 (Clean Water and Sanitation) and SDG 12 (Responsible Consumption and Production).

© 2025This study evaluated the development and characterization of alumina-toughened zirconia (ATZ) composites containing 10 wt% Al2O3 whiskers subjected to the glass infiltration. To obtain ATZ 90/10 composites, the commercial 3Y-TZP powder was mixed with synthesized alumina whiskers and subsequently compacted. Discs (n = 210) were pre-sintered at 1000 °C for 1 h. The infiltration of glass (68SiO2-11.7Al2O3-3CaO-7.3Na2O-10K2O) was developed by mixing glass and propylene glycol, which was then applied onto ATZ pre-sintered specimens. For infiltration, the graded discs were divided into two different sintering protocols: protocol 1 (1550 °C for 2 h) and protocol 2 (1350 °C for 1 h followed by 1550 °C for 2 h). As a control group, non-infiltrated specimens were sintered using protocol 1. The specimens were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. Hardness, fracture toughness, and biaxial flexural strength tests followed by fractographic analysis were performed. Statistical analyses were conducted using Weibull distribution to calculate the material's modulus (m) and characteristic strength (95% CI), as well as ANOVA tests. High-aspect ratio alumina whiskers (10 μm × 200 nm) were synthesized. While the control group's XRD patterns evidenced only characteristic tetragonal zirconia and α−alumina peaks, the glass-infiltrated groups did not present characteristic peaks of crystalline materials. ATZ with alumina whiskers showed higher fracture toughness and characteristic strength compared to conventional ATZ. Furthermore, glass-infiltration improved the characteristic strength of conventional ATZ with no significant differences observed in the Weibull modulus. For W-G-2, C, and W groups the fractures originated at the zirconia surface, while for C-G-1-, C-G-2, and W-G-1 the origins were inside the ceramic microstructure. In conclusion, the development of ATZ with alumina whiskers increased the biaxial flexural strength and fracture toughness compared to conventional ATZ. The glass gradation significantly improved the characteristic strength of conventional ATZ regardless of the sintering protocol used, whereas it only improved the characteristic strength of whisker-reinforced ATZ when a single sintering was performed. Additionally, the sintering protocol influenced the thickness and amount of glass gradation in the composites.

© 2025 Elsevier Inc.Objective: To synthesize bilayer zirconia systems based on commercial or recycled 3Y-TZP obtained from non-milled remnants and to compare their optical and mechanical properties before and after aging. Methods: Bilayer zirconia samples were fabricated using either recycled 3Y-TZP (3Y-R/4Y and 3Y-R/5Y) or commercial powders (3Y/4Y and 3Y/5Y). Microstructure and phase composition were analyzed using ScanningElectronMicroscopy (SEM) and X-Ray Diffraction (XRD). Optical and mechanical properties were assessed via reflectance and biaxial flexural strength tests (BFS), followed by fractographic analysis. Optical properties and BFS data were analyzed using two-way ANOVA and Tukey test, and Weibull statistics, respectively. Results: Recycled powder exhibited particle sizes < 2.07μm. SEM micrographs depicted dense surfaces with largest grains in the 5Y, followed by recycled-3Y, 4Y, and commercial-3Y. XRD analysis revealed tetragonal peaks in commercial and recycled 3Y-TZPs, and tetragonal and cubic phases in the 4Y and 5Y surfaces. Aging induced significant phase transformation in 4Y (∼40 %), commercial- (58 %) and recycled-3Y (53 %), with no effect in 5Y surfaces. Commercial bilayers exhibited higher translucency and strength (∼1130 MPa) compared to recycled bilayers (∼935 MPa), with no significant differences within commercial, nor within recycled groups. Aging decreased contrast ratio for recycled groups and increased the strength of all groups. While all groups presented high reliability up to 500MPa, commercial bilayers outperformed recycled systems at 800-MPa. Significance: The synthesis of bilayered systems using recycled-3Y was successful, resulting in high reliability in missions up to 500MPa. Bilayers based on commercial powder demonstrated superior translucency, strength, and reliability at 800MPa compared to their recycled counterparts.

© 2025 Elsevier Inc.Objectives: To characterize two experimental zirconia bilayer materials compared to their monolithic controls, before and after hydrothermal aging. Methods: Commercial zirconia powders were utilized to fabricate two bilayer materials: 3Y-TZP+ 5Y-PSZ (3Y+5Y/BI) and 4Y-PSZ+ 5Y-PSZ (4Y+5Y/BI), alongside control groups 3Y-TZP (3Y/C), 4Y-PSZ (4Y/C), and 5Y-PSZ (5Y/C). Compacted specimens were sintered (1550 °C- 2 h, 3 °C/min), and half of them underwent hydrothermal aging (134 °C-20h, 2.2 bar). Characterizations were performed through scanning-electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, reflectance tests and biaxial flexural strength test (ISO:6872). Weibull statistics were applied to determine the characteristic strength and Weibull modulus. Grain size and optical properties were analyzed using two-way ANOVA followed by the Tukey test. Results: Degradation regions and monoclinic phase were observed at aged 3Y-TZP and 4Y-PSZ surfaces. Significant differences were observed in the evaluation of optical properties between the bilayer and control groups. The bilayer materials presented intermediate characteristic strength values compared to their controls and aging significantly increased the strength of some groups. Significance: Experimental bilayer materials presented lower mechanical properties than monolithic controls, 3Y/C and 4Y/C. Hydrothermal aging increased the characteristic strength of bilayered and monolithic controls, except for 5Y-PSZ. Both experimental bilayer systems, as well as monolithic controls, met the ISO 6872:2015 requirements for single-unit crowns (100 MPa), 3-unit fixed dental prostheses (FDPs) up to premolars (300 MPa), and 3-unit FDPs involving molars (500 MPa). However, for FDPs with four or more units, only monolithic 3Y-TZP and 4Y-PSZ, and bilayered 3Y+5Y met the required minimum flexural strength (≥800 MPa).

© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.Current approaches for developing bone substitutes prioritize materials with adequate mechanical properties, tailored structures, and resorbing ability under physiological conditions. In this way, new self-setting wollastonite-based apatite cements were prepared by mixing wollastonite powders with a liquid phase containing phosphoric acid and ammonium phosphate in different concentrations. The mixture formed a workable paste that can be molded in different shapes. The cement was analyzed through X-ray diffraction, Fourier Transform Infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy. The analysis showed that the main product of the hydration process is a mixture of crystalline wollastonite and hydroxyapatite. In addition, Raman spectroscopy confirmed the presence of an amorphous phase composed of silica and amorphous calcium phosphate for all samples. The setting times of the cement pastes were measured using a Gilmore needle indentation technique, and the compressive strength was determined using a Universal Testing Machine. The initial setting time was reduced from 142 ± 5 to 10 ± 1 min by increasing 30% of the concentration of phosphate ions in the solution. Furthermore, the higher content of phosphate ions enhanced the compressive strength by 310% compared with cements containing lower concentrations, reaching a resistance of 14 ± 2 MPa. The in vitro biocompatibility was confirmed by MTT assay, wherein no cytotoxicity of the cements was observed against murine embryonic fibroblast cells. Our results provided valuable information for designing wollastonite-based cements with optimal handling, mechanical, and biological properties using a liquid medium with adequate conditions to match the desired final product.

© 2024 Elsevier Ltd3D printing in scaffold production offers a promising approach, enabling precise architectural design that closely mimics the porosity and interconnectivity of natural bone. β-Tricalcium phosphate (β-Ca₃(PO₄)₂, β-TCP), with a chemical composition similar to the inorganic component of bone, is a widely used material for scaffold fabrication. Recent advances have made it possible to functionalize ceramic scaffolds to improve bone regeneration and repair while enabling the in situ release of therapeutic agents to treat bone infections. In this study, 3D-printed β-TCP scaffolds were coated with bioactive glasses, 45S5 (45SiO₂ – 24.5Na₂O – 24.5CaO – 6P₂O₅, wt.%) and 58S (58SiO₂ – 33CaO – 9P₂O₅, wt.%), using sol-gel solutions through a vacuum impregnation technique. The β-TCP ink exhibited pseudoplastic behavior, which facilitated its 3D printing. The resulting scaffolds demonstrated high fidelity to the designed model, featuring well-aligned filaments and minimal collapse of the lower layers after sintering. Elemental mapping revealed that 45S5 glass formed a surface coating around the scaffold struts, whereas 58S glass penetrated the internal structure, this occurred due to their differing viscosities at high temperatures. Compared to uncoated β-TCP scaffolds, the coatings significantly improved mechanical strength, with increases of 63% and 126% for scaffolds coated with 45S5 and 58S, respectively. Bioactivity was confirmed through an apatite mineralization assay in simulated body fluid, which demonstrated hydroxyapatite precipitation on both coated scaffolds, albeit with distinct morphologies. Since this study focused on acellular scaffolds, further research is necessary to fully explore the potential of these bioactive scaffolds with optimized mechanical properties in biological systems.

© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.In the published article, the identification of the samples in the bar chart in Fig. 12 is incorrectly given as CM5, CM6, and CM7: (Figure presented.) Viability of MEF cells cultured in contact with CM1, CM2, and CM3 for 24 h. Solid bars represent the viability of cells cultured directly on the specimens (Group 2), while striped bars show the viability of cells cultured around the specimens (Group 1) next to the samples. One-way ANOVA test significance levels **p < 0.01 and ***p < 0.0005 The correct identification on bar chart should be CM1, CM2, and CM3, respectively as showed below in Fig. 12: (Figure presented.) Viability of MEF cells cultured in contact with CM1, CM2, and CM3 for 24 h. Solid bars represent the viability of cells cultured directly on the specimens (Group 2), while striped bars show the viability of cells cultured around the specimens (Group 1) next to the samples. One-way ANOVA test significance levels **p < 0.01 and ***p < 0.0005 The original article has been corrected.

© 2024 Elsevier Ltd and Techna Group S.r.l.To evaluate the mechanical, antimicrobial, and optical properties of boron-doped soda-lime glass coatings on 3Y-TZP and 5Y-PSZ zirconia. Disc-shaped specimens of 3Y-TZP and 5Y-PSZ were divided into: as-sintered (3Y-C and 5Y-C), coated with commercial glaze (3Y-G and 5Y-G), with soda-lime glass (3Y-SL and 5Y-SL), and with silver-containing soda-lime glass (3Y-SLAg and 5Y-SLAg). Cytotoxicity (MTT assay), biaxial flexural strength (σB), X-ray diffraction (XRD), translucency (TP00), color difference (ΔE00), and roughness (Ra and Rz) were conducted. Biofilm formation was quantified by colony-forming units (CFU/mL) of C. albicans, S. sanguinis, and E. coli. Scanning electron microscopy (SEM) and fractography were conducted. Energy-dispersive X-ray diffraction (EDS) was performed on SL and SLAg samples. Weibull modulus (m) and characteristic strength (σ0) for biaxial flexural strength (95 % CI) were calculated. All data were analyzed by two-way ANOVA, and Dunn's method, while the CFU test was analyzed by one-way ANOVA (α = 0.05). The experimental glasses did not induce cytotoxic effects. The flexural strength of 3Y-TZP groups showed highest values: 3Y-C(847.45 MPa); 3Y-G(843.22 MPa); 3Y-SL(806.41 MPa); 3Y-SLAg(769.04 MPa); 5Y-G(589.77 MPa); 5Y-SLAg (576.20 MPa); 5Y-C(479.44 MPa); 5Y-SL(474.00 MPa). Diffractograms showed tetragonal and cubic phases for all groups. Higher translucency values were observed for 5Y-PSZ groups, while for ΔE00 were similar. The SL and SLAg groups exhibited the lowest roughness values (Ra) for both zirconia. The 5Y-SL group exhibited antimicrobial effects against all tested microorganisms, while the 5Y-SLAg group showed antimicrobial effects against E. coli. Fractures originated at the zirconia surface, while for the 5Y-G group at the glaze layer. SEM micrographs revealed flower-shaped crystals for 3Y-SL, 5Y-SL and 5Y-SLAg groups. EDS identified zirconia in the crystal's composition. The 5Y-SL group exhibited a significant antimicrobial effect. This cytocompatible glass (5Y-SL) provided a superior antibiofilm effect compared to 5Y-SLAg. Moreover, the mechanical and optical properties of both 5Y-PSZ and 3Y-TZP zirconia were maintained.

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2025.Cooling systems play a critical role in maintaining operational efficiency and reducing emissions from automotive vehicles. Given the increasing demand for more efficient and environmentally friendly vehicles, optimization of radiators, which are the central components of these systems, is essential. This study proposes the prediction of the thermo-hydraulic performance and second-law analysis of porous-media radiators through CFD modeling. The flow was solved using the finite-volume method for various geometries and inlet mass flow rates, followed by further thermodynamic analysis. The findings revealed that increases in both the coolant mass flow and the radiator’s frontal area significantly enhanced heat transfer. However, these improvements also result in increased entropy generation, highlighting the complex balance between the thermal efficiency and thermodynamic irreversibility. Also, higher PPI improves heat transfer by increasing surface area but causes greater thermodynamic inefficiencies due to higher flow resistance and pressure gradients. In contrast, higher porosity reduces flow resistance, enabling smoother fluid flow and lowering entropy generation. This study emphasizes the significance of entropy generation analysis, demonstrating that modifications in radiator geometry and operational conditions can profoundly affect both the energy efficiency and operational sustainability of automotive systems. The database that emerges from this procedure is then used to search for the best geometry and mass flow rate, based on the entropy generation number and heat exchanger effectiveness.

© 2024 Elsevier LtdThis study explored the challenge of managing overheating in scramjet engines through regenerative cooling techniques using hydrogen as a coolant. The aim was to reduce the high temperatures between the airflow and compression ramps at the scramjet inlet by affixing small-scale channels to the engine wall. The modeling process involved a two-dimensional CFD) simulation for the scramjet inlet and discretization of each cooling jacket channel into duct elements. After obtaining the CFD flow solution, the wall heat flux distribution was incorporated into the cooling channel model, initiating a forward marching procedure to compute the temperature and pressure distributions. The converged distributions are then used to calculate the entropy generation rates along the cooling jacket. The simulations demonstrate that higher Reynolds numbers lead to increased thermodynamic losses despite the improved heat transfer efficiency. Conversely, lower altitudes contribute to higher entropy generation rates owing to increased heat generation from flow compressibility and amplified flow acceleration. Additionally, higher Mach numbers intensify the entropy generation, resulting in elevated heat fluxes at the scramjet wall. Considering the entropy generation rate as an objective function that must be minimized, an optimum coolant mass flow rate can be achieved for different freestream airflow conditions. It is evident that implementing channel-specific geometry with second-law analysis is an appropriate strategy for mitigating extreme wall temperatures, thereby enhancing the performance and prolonging the service life of scramjet engines.

© 2025 Elsevier LtdThis work explores the use of thermoelectric coolers (TECs) for managing the temperature of aircraft electronics. TECs offer advantages over traditional compressor-based systems, including compactness, lower weight, and the capability to cool below ambient temperatures, making them ideal for aerospace applications. A novel method for estimating thermoelectric coefficients was developed, leveraging optimization to improve accuracy. Simulation models were created using Amesim to predict TEC performance under varying conditions and validated through laboratory experiments, achieving a maximum steady-state error of 1.97 °C. Simulations under flight conditions demonstrated the system's effectiveness in maintaining electronics enclosure temperatures well below limits. With a constant 12 V supply, the load temperature stayed under 40 °C during the flight, dropping below 30 °C by the end. However, heat dissipation increased significantly, averaging 573 W, with peaks up to six times the load's thermal dissipation when no voltage control was applied. These results confirm the feasibility of TECs for aerospace thermal management, particularly for electronics requiring strict temperature control.

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2025.Optimizing the energy conversion processes within aircraft and developing novel aircraft configurations have become imperative for fostering a more sustainable aviation sector. Exergy analysis emerges as a valuable tool in pinpointing areas for improvement and evaluating innovative configurations. The present work intends to expand upon the exergy concept in the assessment of airfoil aerodynamics. This is achieved through drag breakdown and flow field analysis utilizing the exergetic method. The study employs computational fluid dynamics analysis, utilizing the airfoil NACA 0012 for subsonic compressible flow and NACA 2315, NACA 2312, and NACA 2309 for transonic compressible flow as test cases to illustrate the concept. Rates of exergy destruction and a thorough flow field analysis are presented along the wake downstream of the airfoil, comparing four turbulence models. The theoretical exergy method is juxtaposed with the classical near-field method and validated through technical reports. Ultimately, the findings indicate a potential for improvement using the exergy method in aerodynamics, resulting in a 12% reduction in drag in a 2D flow field, translating into potential energy savings up to 31000 W. Furthermore, it is also demonstrated that the impact of airfoil thickness variation on exergy destruction in the transonic regime is found to be negligible.

© 2025 The AuthorsThe present work performs a review for using hydrogen in aircraft propulsion systems analyzing challenges and opportunities with the two main driveline architectures: direct combustion of hydrogen and fuel cells. First, the capability of hydrogen aircraft to become more energy efficient than conventional aircraft are discussed on system level, by extending previous review work. Then, challenges for hydrogen combustion and ways to limit emissions by lean direct injection and micromix combustion are discussed. Polymer electrolyte membrane (PEM) and solid oxide fuel cells are reviewed and the outlook for high temperature PEM fuel cells and challenges with per- and polyfluoroalkyl substances (PFAS) emissions are discussed. Dual fuel aircraft and flexible combustion are discussed as ways to provide a transition to a hydrogen economy. Additionally, hybrid configurations and new cycles that simplify hydrogen integration are reviewed. Finally, recent promising results on water emissions and contrail formation for hydrogen combusting aircraft are discussed.

© 2025 Emerald Publishing LimitedPurpose – This paper aims to assess the feasibility of using additive manufacturing (AM) to produce a gas-turbine’s fuel swirler, thereby validating its suitability for this fabrication process. This study involves a statistical comparison of the AM process with other manufacturing methods, utilizing a multi-criteria decision-making approach to determine the most favorable method for the component. This study also includes the manufacturing of the component and an evolution of the quality control results to ascertain the component’s compliance with required standards. Design/methodology/approach – To compare the different fabrication methods, this paper uses the analytic hierarchy process to compare AM with alternative manufacturing processes, generating different scenarios for comparison. In addition, two samples of the component were additively manufactured to assess their suitability for application in a small gas turbine. Findings – The results indicate that AM was identified as eligible and adequate process for producing the fuel swirler in most scenarios. This study includes the results of a nondestructive quality control process and provides a comprehensive discussion aiming to optimize the component’s quality. These results support the potential for scaling up the production of this component and identifying other components that may benefit from AM. Originality/value – This research contributes to the advancement of technical knowledge regarding the application of an innovative manufacturing method for jet engine components. It aims to enhance manufacturing capabilities for different thermal machine parts while reducing design costs.

© 2025 by the authors.Adverse pressure gradients are intrinsic to compressor flow behavior and are further intensified by secondary effects associated with rotor tip clearance flow interactions. Tip clearance generates leakage flow, which leads to the formation of tip leakage vortices, a major contributor to aerodynamic losses in axial compressors. These vortices significantly influence both compressor performance and operational stability. Extensive prior research has demonstrated that passive casing treatments, particularly axial slots, can substantially improve the stall margin in axial compressors. In this work, the performance of a new casing treatment geometry is investigated using the concept of recirculating flow within semi-circular axial slots. The proposed casing treatment geometry builds upon recent experimental findings involving single-rotor configurations. It was applied to the first rotor row of a three-and-a-half-stage (3.5-stage) axial compressor comprising an inlet guide vane followed by three rotor–stator stages. The numerical model incorporates axial slots with a novel periodic interface approach implemented in a multistage compressor simulation. Three-dimensional steady-state RANS (Reynolds Average Navier-Stokes) simulations were performed to investigate the aerodynamic effects of the casing treatment across various rotational speeds. The results for the casing treatment configuration were compared with those of a baseline smooth casing. The introduction of the new casing treatment produced noticeable modifications to the internal flow structure, particularly in the tip region, resulting in improved overall compressor stability within the operating range of 85 to 100% of design speed.

© 2025 by the authors.Turbines are rotating machines that generate power by the expansion of a fluid; due to their characteristics, these turbomachines are widely applied in aerospace propulsion systems. Due to the clearance between the rotor blade tip and casing, there is a leakage flow from the blade pressure to the suction sides, which generates energy loss. There are different strategies that can be applied to avoid part of this loss; one of them is the application of so-called desensitization techniques. The application of these techniques on gas turbines has been widely evaluated; however, there is a lack of analyses of hydraulic turbines. This study is a continuation of earlier analyses conducted during the first stage of the hydraulic axial turbine used in the low-pressure oxidizer turbopump (LPOTP) of the space shuttle main engine (SSME). The previous work analyzed the application of squealer geometries at the rotor tip. In the present paper, winglet geometry techniques are investigated based on three-dimensional flowfield calculations. The commercial CFX v.19.2 and ICEM v.19.2 software were used, respectively, on the numerical simulations and computational mesh generation. Experimental results published by the National Aeronautics and Space Administration (NASA) and data from previous works were used on the computational model validation. The parametric analysis was conducted by varying the thickness and width of the winglet. The results obtained show that by increasing the winglet thickness, the stage efficiency is also increased. However, the geometric dimension of its width has minimal impact on this result. An average efficiency increase of 2.0% was observed across the entire turbine operational range. In the case of the squealer, for the design point, the maximum efficiency improvement was 1.62%, compared to the current improvement of 2.23% using the winglet desensitization technique. It was found that the proposed geometries application also changes the cavitation occurrence along the stage, which is a relevant result, since it can impact the turbine life cycle.

Copyright © 2025 by ASME.Due to the growing relevance of mitigating climate change, and the race to improve the energy efficiency of aircrafts, aiming a goal of net-zero emissions of CO2 by 2050, the aircraft propellers have been receiving more attention, as they could represent the next innovation towards the efficiency improvements, especially due to the possibility of hybrid/electrical propulsion. In this context, this article consists of a critical overview of propeller design methods, depicting some relevant classical methods of designing propellers, such as the Blade Element Momentum Theory by Glauert, Vortex Theories, developed by Betz, Goldstein, and Theodorsen, as well as methods to design propellers that are intended to increase the lift on the wings. The straightforward Propeller Design procedures by Larrabee, Adkins Liebeck, and Wald, which are based on these theories, are also covered and compared. In addition, this paper also covers the final design and optimization, showing how computational methods, such as VLM and CFD, are being used in the literature to improve preliminary designs and model the interaction between the propellers and the wing/body. The objective of this paper is to provide a comprehensive reference for researchers and students, summarizing the state-of-Art of propeller design and optimization, for those who intend to work with propellers for green aviation.

© 2025Alginate hydrogels are extensively utilized as a foundation for bioink formulations due to their facile gelation properties. In this study, the rheological behavior of alginate cross-linked by various biologically relevant ions was systematically investigated, with an emphasis on bioink development for bioprinting applications. While the cross-linking of alginate by calcium (Ca2+) ions is well-established, this work explored the effects of other divalent alkaline earth ions, including magnesium (Mg2+), strontium (Sr2+), and barium (Ba2+), as well as trivalent ions iron (Fe3+) and lanthanum (La3+), and the monovalent ion cesium (Cs+). Rotational and oscillatory rheological tests were performed to assess the gelation behavior and mechanical properties of the hydrogels. The findings demonstrated that alginate gelation is influenced not only by ion valency but also by charge density. Among the divalent ions, Mg2+ failed to cross-link alginate chains effectively, whereas Ba2+ produced hydrogels with superior rheological properties. The trivalent ions, Fe3+ and La3+, induced gelation at relatively low concentrations, highlighting the role of charge density in enhancing cross-linking efficiency. In contrast, the monovalent ion Cs+, with its low charge density, did not promote hydrogel formation. These results were critically analyzed in the context of bioprinting requirements, emphasizing the importance of ion selection for tailoring bioink properties to meet the mechanical and structural demands of bioprinting processes.

© 2025 The Authors. Published by American Chemical Society.Nanocellulose-based materials have been widely used to encapsulate and release drugs due to their biocompatibility, high drug-loading capacity, and controllable release profiles. However, effective administration of hydrophobic drugs remains challenging due to the water-insoluble organic compounds that make up many currently available drugs (e.g., anti-inflammatory or anticancer drugs). Here, we developed a pH-responsive coated bacterial cellulose (BC) capsule loaded with the hydrophobic drug curcumin (Cur) as a proof of concept for delivering targeted hydrophobic drugs to the colon. Cur was encapsulated in the hydrophilic capsule through an osmotic gradient phenomenon and then coated with carboxymethyl chitosan. The coating was carried out by adding calcium chloride, which facilitates the cross-linking of carboxymethyl chitosan, forming a stable protective layer. In vitro release analysis using the gastrointestinal medium revealed that the BC capsule coated with the pH-sensitive polymer carboxymethyl chitosan had a release profile activated by pH 6.8, providing efficient and protecting loads from premature release. In vitro experiments were performed with HT29 cells and showed that capsules loaded with Cur were more toxic to cancer cells. Overall, the proposed scalable, inexpensive, and simple manufacturing method has great potential for advanced biomedical applications including targeted therapy for hydrophobic drug delivery.

© 2024 Elsevier LtdBone tissue engineering (BTE) aims to address critical challenges in bone regeneration caused by trauma, diseases, or age-related degeneration. Despite the inherent regenerative capacity of bone tissue, large or complex defects often exceed the body's ability to heal effectively. This paper explores the development and characterization of printed poly-lactic acid and multifunctional bioactive glass (PLA/MFBG) composites as potential solutions for enhancing bone regeneration strategies. Bioactive glasses, known for their biocompatibility and osteogenic properties, were synthesized via a sol-gel route. The synthesis incorporated essential ions (Si, Ca, P, Cu, Sr, Mg, Zn) crucial for bone formation. The improved mechanical and biological properties required for effective bone substitutes were achieved by the integration of MFBG into PLA matrices using fused deposition modeling (FDM), e.g., a cost-effective 3D printing technique suitable for large-scale scaffold production. The composite materials exhibited enhanced physico-chemical properties, along with improved mechanical strength, controlled biodegradation, and superior biocompatibility, underscoring their potential for advanced BTE applications. This research underscores the potential of integrating multifunctional bioactive glass into polymer matrices as a viable approach to overcome current limitations in bone tissue engineering. It paves the way for future advancements in medical and dental therapies.

© 2025 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.Energy conversion materials represent a rapidly evolving field that is core to future sustainable technologies. Caloric effect materials, which convert magnetic, electrical, or mechanical stress into thermal energy, are particularly promising for their potential application in solid-state cooling. In particular, the torsiocaloric effect—where materials convert pure shear stress into thermal energy—remains relatively underexplored despite its immense technological potential. However, progress in this area has been hindered by the lack of commercial instrumentation designed to study the thermomechanical properties of materials under shear stress. In this work, we present a device capable of characterizing materials under shear stress and directly measuring the torsiocaloric effect efficiently. The system was tested using two distinct materials—a rigid polymer and a shape memory alloy—demonstrating its versatility. Our results show that the device can successfully generate torque versus angular displacement curves, conduct fatigue tests, measure adiabatic temperature change, and evaluate caloric reversibility. These outcomes highlight the device’s excellent performance and its potential to advance the research in the torsiocaloric field.

© 2025 by the authors.Blast mitigation of structures is an important research topic due to increasing intentional and accidental human-induced threats and hazards. This research area is essential to building capabilities in sustaining structural protection, site planning, protective design efficiency, occupant safety, and response and recovery plans. This paper investigates experimental tests and finite element analysis (FEM) of thin A36 steel sheets subjected to blast. Six field blast tests were performed at standoff distances of 300 mm and 500 mm. The explosive charges comprised 334 g of bare Composition B, and the steel sheets were 2 mm thick. The experimental results, derived from the analysis of high-speed camera recordings of the blast events, were compared with FEM simulations conducted using Abaqus®/Explicit version 6.10. Three constitutive material models were considered in these simulations. First, the FEM simulation results were compared with experimental results. It was shown that the FEM analysis provided reliable results and was proven to be robust and cost-effective. Second, an extensive set of 460 additional numerical simulations was carried out as a parametric study involving varying standoff distances and steel sheet thicknesses. The results and methodologies presented in this paper offer valuable and original insights for engineers and researchers aiming to predict damage to steel structures during real detonation events and to design blast-resistant structures.

© 2025 by the authors.Structural research teams face significant challenges when conducting studies with explosives, including the costs and inherent risks associated with field detonation tests. This study presents a replicable method for loading spherical and bare TNT-based cast explosive charges, offering reduced costs and minimal risks. Over eighty TNT and Composition B charges (comprising 60% RDX, 39% TNT, and 1% wax) were prepared using spherical molds made of thin aluminum, which are low-cost, off-the-shelf solutions. The charges were bare, meaning they lacked any casing, as the molds were designed to be easily removed after casting. The resulting charges were safer due to their smaller dimensions and the absence of hazardous metallic debris. Composition B charges demonstrated promising results, with their performance characterized through blast and thermochemical experiments. Comprehensive data are provided for Composition B charges, including TNT equivalence, pressures, velocity of detonation, DSC/TGA curves at four different heating rates, activation energy, peak decomposition temperatures, X-ray analysis, and statistics on masses and densities. A comparison between detonation and deflagration processes, captured in high-speed footage, is also presented. This explosive characterization is crucial for structural teams to precisely understand the blast loads produced, ensuring a clear and accurate knowledge of the forces acting on structures.

© 2025 by the authors.In recent years, a series of studies have examined the effects of blast loads on structures and proposed new materials to enhance or retrofit the resistance of conventional materials, such as steel or concrete. Polymeric materials, including foams and elastomers, play a significant role in this field due to their low density and favorable mechanical properties under dynamic loads. This study investigates the use of polyurethane elastomer to improve the mechanical properties of 2 mm A36 steel sheets. The efficiency of this material in steel structures has not yet been studied in the scientific literature through blast tests. A total of 18 near-field blast tests were conducted at standoff distances of 300 mm and 500 mm. The explosive charges consisted of 334 g of bare Composition B in a spherical shape. The steel sheets were fixed to rigid supports and exposed to the blast either bare or covered with different layers of commercial Shore A 60 or 90 polyurethane elastomer, with thicknesses varying from 2 to 6 mm. The maximum displacement of the steel sheets was measured using a high-speed camera and the results were compared. The elastomer retrofitted sheets exhibited a reduction in maximum displacement ranging from 5% to 20% when compared to the sheet without the elastomer.

© 2025 Academia Brasileira de Ciencias. All rights reserved.The N5⁻ anion, known as pentazolate, represents a groundbreaking advancement in the field of energetic materials, offering promising applications in rocket propulsion, explosive devices, and pyrotechnics. Comprising five nitrogen atoms arranged in a cyclic structure with a negative charge, has captured significant interest due to its unique configuration and high energy potential. In this article, we provide a comprehensive overview of the N5⁻ anion’s potential as an energetic material, alongside the role of RMD simulations in elucidating its behavior. The ReaxFF forcefield was used to simulate the materials pyrolysis. The total energy behavior of different species containing pentazolate, across a range of temperatures (1500 K to 3000 K) revealed distinct trends and characteristics associated with the thermal dynamics and stability of the molecule under varying thermal conditions. Their mechanisms were elucidated, and the kinetic parameters were calculated, indicating that CNN5, with its low activation energy (39.14 kJ/mol), stands out as the most reactive, while PolyN5, with the highest activation energy (52.88 kJ/mol), is the most stable. Overall, the N5- anion represents a promising avenue for the development of high-energy materials.

© 2025 Elsevier B.V.This study investigates the grain refining efficiency and fading mechanisms of a 4Nb-1B-Al master alloy in an AA 413 eutectic aluminum-silicon alloy, comparing its performance to that of a conventional 5Ti-1B-Al refiner. The Nb-based refiner produced significantly finer grains—reducing the average grain size by approximately 200 µm after 15 min—and maintained superior performance even after 60 min. The enhanced refinement was attributed to the presence of Al₃Nb particles, which dissolve more slowly than Al₃Ti, as evidenced by thermal analysis and microstructural characterization. In unstirred melts, sedimentation and agglomeration of Al₃Nb and NbB particles were observed, indicating key fading mechanisms. These effects were mitigated by vigorous melt stirring and reduced holding times. Unlike Ti-based refiners, the Nb-based refiner showed no evidence of silicide formation (commonly referred to as grain poisoning). These results underscore the potential of Nb-based refiners for high-Si aluminum alloys, provided that processing conditions are optimized to minimize fading.

© 2025 Elsevier Inc.Martensite to austenite reversion was investigated in cryorolled AISI 317 L austenitic stainless steel. The material was rolled at 77 K to a thickness reduction of 50 % and subjected to isothermal annealing for 1 h from 200 to 1100 °C, as well as continuous annealing up to 1000 °C. Austenite reversion was followed by several characterization techniques including dilatometry, differential scanning calorimetry (DSC), X-ray diffraction (XRD), Vickers microhardness testing, DC-magnetization, light optical (LOM) and scanning electron (SEM) microscopy, high-resolution electron backscatter diffraction (EBSD), energy-dispersive X-ray spectroscopy (EDS), and electron channeling contrast imaging (ECCI). Dilatometric, calorimetric and magnetization measurements show that αˈ-martensite to austenite reversion occurs within the temperature range of 400–700 °C. The reversion of ε-martensite occurs between 300 and 400 °C. In the range of 700–900 °C sigma (σ) and chi (χ) phases precipitate within δ-ferrite. Full recrystallization and dissolution of σ and χ precipitates take place around 1000 °C. After reversion, austenite has the same texture components of cryorolled state; i.e., Brass, Goss and S components. The persistent morphology of the deformation microstructure up to 700 °C, as well as few changes in texture, point to a displacive reversion mechanism. The temperature for shear-dominated reversion estimated by thermodynamic calculations is approximately 526 °C. By choosing a proper temperature window and annealing time, the reversion of martensite to austenite leads to a quasi-bimodal austenite grain size distribution, which helps overcome the tradeoff between strength and ductility.

© ASM International 2024.Precipitation hardening (PH) martensitic stainless steels, such as 17-4, have been investigated for use in additive manufacturing (AM) techniques to produce parts with complex and individualized geometries, finding wide use in the aerospace, petrochemical, nuclear, and marine industries due to their high mechanical strength and corrosion resistance. However, AM can result in a material with the presence of porosities, segregations and metastable phases. Thus, the aim of this research is to study the microstructure evolution and corrosion resistance of 17-4 PH processed by laser powder bed fusion (LPBF) in comparison with conventional processing, under thermal treatment, as-built, and after AM processing with thermal treatment conditions. The findings of this study show that the AM-processed material exhibits a microstructure with a fish scale-like morphology, smaller grain size and higher fraction of retained austenite, characteristics that are modified after solubilization treatment, although the hardness remains higher than that observed in conventional processing. The corrosion test results showed that the samples treated after AM processing present a corrosion resistance close to the samples only thermally treated.

© 2025 by the authors.Directed Energy Deposition-Laser Beam (DED-LB) is an ideal Additive Manufacturing (AM) process to obtain very complex geometries, which can be important for several applications in industries such as aerospace and biomedical engineering. The present study aims to determine optimized DED-LB parameters for printing 17-7 PH stainless steel, a semi-austenitic precipitation-hardening alloy renowned for its exceptional combination of high yield strength, toughness, and corrosion resistance. The experimental work used different combinations of laser power, scanning speed, and powder feed rate to investigate the effects on the morphology, surface roughness, and microstructure of the deposited material. The results indicated that a powder feed rate of 4.7 g/min yielded uniform beads, reduced surface roughness, and increased substrate dilution, enhancing the metallurgical bond between the bead and substrate. Conversely, higher feed rates, such as a rate of 9.2 g/min, resulted in increased surface irregularities due to an excessive amount of partially melted powder particles. Microstructural analysis, supported by thermodynamic calculations, confirmed a ferritic–austenitic solidification mode. The austenite and ferrite fractions varied significantly, depending mainly on the substrate dilution due to the decrease in aluminum content. The combination of 400 W laser power and a 2000 mm/min scanning speed resulted in the optimal set of parameters, with an approximately 30% dilution and 80% austenite.

© IMechE 2025Ducted fuel injection (DFI) is a promising technology that can modify the combustion process in compression ignition engines to mitigate soot formation. By guiding the spray through ducts, air entrainment is enhanced, promoting a more pronounced premixed combustion phase, reducing the diffusion flame, and consequently suppressing soot generation. While previous studies using constant-volume chambers and optical research engines have demonstrated the potential of DFI and the influence of injector geometry on emissions, few have implemented this approach directly in engines due to the substantial modifications required to the cylinder head. This study proposes and evaluates an alternative DFI configuration suitable for light-duty compression ignition engines, implemented without significant modifications to the engine head. Experiments were conducted in a single-cylinder research engine using a sleeve fitted to the injector, aligning the ducts with the nozzle holes. The limited space introduces constraints such as a trade-off between duct length and stand-off distance, and a duct length shorter than the theoretical liquid penetration length. Results show that the configuration with a 3.5 mm stand-off distance achieved up to a 70% reduction in soot emissions compared to the free-spray baseline, while shorter stand-off distances (2.5 and 3.0 mm) were less effective. Although DFI delays ignition, it enhances air entrainment and premixed combustion, ultimately accelerating the combustion process.

© 2025 IEEE.The adoption of robots for everyday tasks has surged, fueled by technological advancements. Contemporary robotic designs focus on expanding operational workspaces, enhancing flexibility, and overcoming challenges such as singularities. Successful task execution depends on the effective integration of robust hardware and software. Key hardware considerations include the design of links for reach and the connection of joints to motors, drivers, and sensors. The software serves as an interface for controlling these components and must accurately reflect the robot's kinematics. Effective communication between hardware and software is essential for optimal operation. While commercial software often conflicts with unconventional robotic designs, open-source solutions like Robot Operating System (ROS) provide greater flexibility and a wide range of tools, although they can encounter difficulties in interfacing with commercial hardware. This paper evaluates two communication protocols, Automation Device Specification (ADS) and User Data-gram Protocol (UDP), for integrating ROS2 with the commercial software TwinCAT from Beckhoff. The integration was assessed using both ADS and UDP protocols, with UDP demonstrating superior effectiveness. Then, the integration was applied in a real robot. The system employs ROS2 tools such as RVIZ2 for real-time monitoring and MoveIt2 for inverse kinematics calculations, while TwinCAT receives information from ROS2 through the UDP protocol and sends it to the drivers. This study highlights the critical importance of choosing appropriate communication protocols for advanced robotic systems. By confirming UDP's enhanced performance in practical scenarios, this research lays the groundwork for future developments in robotics that require seamless integration between hardware and software.

© 2025 COSPARThis work describes the development of a semi-analytic theory for a preliminary orbit analysis of the GARATÉA-L Brazilian lunar probe. The dynamical model includes the effects of the zonal harmonics J2 up to J12, the effects of second- and third-degree tesserals and sectorials, and the third-body perturbation due to the attraction of the Earth. The Hamiltonian describing the dynamics is implicitly expressed in Delaunay variables, and, Hori's method is applied to derive a semi-analytic solution which is expressed in closed form with respect to the eccentricity. Expressions for Keplerian orbital elements are obtained including short-period and medium-period terms. In order to avoid singularities in eccentricity, non-singular orbital elements are introduced to compute frozen orbit conditions considering several values of inclinations and semi-major axes. A preliminary analysis of the orbit of the GARATÉA-L Brazilian probe is conducted, and the results are compared to those provided by several models using Cowell's method. A realistic model based on ephemeris data is also used for comparison. The findings reveal that the probe's nominal orbit does not exhibit a frozen condition in terms of eccentricity. A new inclination is proposed to freeze the orbit without altering the pericenter and apocenter altitudes. However, orbital evolution results in a collision with the Moon, as revealed by the 50 × 50 models. A polar frozen orbit is then suggested, offering the advantage of gradually shifting the sub-pericenter point from the South Pole toward the center of the Aitken Basin region.

© CSP - Cambridge, UK; I&S - Florida, USA, 2025.The goal of this research is to develop a battery model using experimental data gathered during the discharge of a lead-acid battery. It is essential to develop a mathematical model that accurately depicts the system in order to precisely describe the electrical characteristics of the battery and examine its discharge behavior while it is operating. The identification of an electrical model for a lead-acid battery using the data gathered in this manner is presented in this study. Jackey’s model was selected to depict the battery dynamics due to its resistive and capacitive properties, as well as the fact that it fits the experimental data well and has the advantage of being reasonably complex. The objective is to identify Jackey’s model parameters by using optimization techniques. In the end, the findings show that the selected mathematical model fairly depicts the system, which makes it a good substitute for lead-acid battery mathematical modeling.

© The Author(s), under exclusive licence to Springer Nature Singapore Pte Ltd. 2025.The objective of this study is to present an experimental procedure for identifying the dynamics of an unmanned aerial system (UAS) with a fixed flexible wing. This procedure employs subspace identification techniques, which are particularly suited to the analysis of dynamic systems. In order to comprehend the behaviour of aerodynamic and flight control systems and establish a feedback loop that may be employed to mitigate the impact of structural flexibility, it is imperative to possess a reliable model. The objective of this research is to identify a parametric model for a flexible aircraft from open-loop experimental data by applying the DSRe algorithm. A flight test campaign was conducted using the EOLO, a single-engine aircraft with a wingspan of 4 m and a total weight of 8.87 kg. First, the results of the identification process using synthetic data are presented. The preliminary estimated parameters based on the Ground Vibration Test (GVT) were found to be useful for validating the identified model. Subsequently, the experimental results obtained in open-loop operation demonstrate that subspace algorithms are capable of estimating a suitable state-space model that encompasses the entire frequency range present in the experimental data. It is crucial to emphasise that a significant challenge in developing a representative model for the desired frequency range from the collected data is the necessity for a persistently exciting condition for the input signals.

© The Author(s), under exclusive licence to Springer Nature B.V. 2025.This paper presents a comprehensive modeling framework for turbulent flow and phase-change phenomena in porous media. The study revisits the double-decomposition concept for macroscopic turbulence modeling, where instantaneous variables are averaged in both time and space, leading to distinct forms of the governing equations. The model extends the “One-Energy Equation Model” to simulate melting and solidification of pure substances and alloys, treating the solid phase as a porous medium with low porosity and permeability. During phase transition, thermal equilibrium is assumed in the mushy zone, while viscous and form drag effects are adjusted based on temperature. The latent heat is treated implicitly in the energy equation, and the liquid fraction is updated iteratively. Numerical solutions employ the SIMPLE algorithm with the Strong Implicit Procedure for inner iterations. Validation against existing literature demonstrates the model’s accuracy for pure substances.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The global shift to a carbon-free economy has spurred innovative technologies while necessitating the decommissioning of outdated energy infrastructure, including oil and gas wells. Strict environmental regulations now mandate that abandoned wells undergo plug and abandonment (P&A) operations to prevent future leaks. With thousands of wells still in operation and the rising costs of P&A, the industry is exploring more reliable, cost-effective solutions to address the impending "P&A wave." One promising technique involves using a powerful heat source to melt the casing, tubing, and surrounding rock at the plugging site, creating a seal upon cooling. This article presents a mathematical model and simulations of the reaction front propagation in a thermite mixture ignited in a vertical tube. Preliminary results show good qualitative agreement with experimental data, highlighting the potential of this method for improving P&A operations.

© 2025, Begell House Inc.. All rights reserved.This paper presents a novel numerical approach for addressing the phase change term in the energy equation. The One-Energy Equation Model (1EEM) is extended to handle both melting and solidification processes for pure substances and alloys. Prior to melting and after solidification, the solid material is modeled as a porous medium with low porosity and minimal permeability. During phase transition, thermal equilibrium is assumed in the mushy zone. As the temperature surpasses the melting point, viscous and form drags in the momentum equation decrease. Latent heat is discretized using a combination of implicit and explicit methods in the energy equation. After computing the temperature field, the liquid fraction is updated across the domain. The algebraic systems are solved using the SIMPLE algorithm, with inner iterations utilizing the Strong Implicit Procedure. Initial findings show that the model produces results consistent with those found in the literature.

© 2025 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.Correction Notice Please write out the details of your corrections here. Place any figure, image, or math updates as well. Be as specific as possible and refer to the original paper details. Please see an example of a correction here: https://arc.aiaa.org/doi/10.2514/6.crossmarktest.c1 The correct first name of second author is “Kesiany” instead of “Kasiany”.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.Impact damage to composite structures results in multiple, complex failure modes, often requiring the replacement of entire components and thereby escalating aircraft maintenance costs. To address this issue, the present study investigates the damage propagation behaviour with particular emphasis on intra- and interlaminar failure modes. Carbon fibre/epoxy composites were subjected to tensile after impact (TAI) fatigue tests at different energy levels to induce different damage modes and extents within the specimens. A non-destructive testing technique (C-scan) was used to assess the interlaminar damage propagation, while the intralaminar fracture toughness of the post-impact specimens was characterised using a finite fracture mechanics model. The results show that the crack propagation behaviour is strongly influenced by the initial impact damage characteristics, in particular the impact energy level. Lower impact energies tend to promote interlaminar failure modes leading to fatigue crack propagation by delamination. Conversely, higher impact energy levels induce fibre fracture, resulting in a self-similar relationship between intra- and interlaminar propagation.

© 2025 Elsevier LtdAdhesive bonding technologies for thermoset polymer composites have been used in marine, automotive, construction and aerospace industries due to their superior mechanical behaviour (high strength-to-weight ratio, damage tolerance and fatigue resistance) compared to conventional joining methods. The main disadvantage of this joining technology is its susceptibility to delamination due to disbonding during use. Loading conditions, adhesive type, ageing effects and lack of inspection procedures are just some of the elements that affect the overall structural performance of the composite joint during the manufacturing process. A deeper understanding of how these elements affect joint behaviour is required to improve joint performance and design. This work provides a comparative fractographic analysis for two different joint types: co-bonded (CB) and secondary bonded (SB) joints, under Mode I delamination at elevated temperature and high humidity conditions. Fractographic analysis was used to compare the two joint technologies and explain the differences in toughness values and fracture behaviour, revealing crack propagation mechanisms in composite joints. While the CB and SB joints have comparable fracture toughness (GIC) values, different fracture characteristics and bonding methods can discern these two bonding technologies, indicating that SB joints are more susceptible to environmental conditioning.

© 2025The design of damage-tolerant aeronautical composite structures often involves thin-walled components that are susceptible to in-plane mixed-mode fracture. Unlike with metals, this process is complicated by the composites anisotropy and the lack of standardized procedures for predicting failure in notched, holed or cracked composites under mixed-mode loading. This study introduces a novel Modified Arcan Fixture (MAF) for testing Compact Tension Shear (CTS) specimens of carbon fibre woven reinforced polymer composite. Digital Image Correlation (DIC) was used to capture strain fields and calculate Stress Intensity Factors (SIFs), which were then compared to analytical predictions for different mode combinations and notch lengths. R-curves were generated for specimens exhibiting self-similar crack propagation. The results revealed that failure modes were dominated by tensile cracking in Mode I and compressive cracking in Mode II, indicating that a single-parameter fracture criterion inadequate for the failure description. A theoretical model that incorporates both tensile and compressive cracking is proposed, which can accurately predict the complete mixed-mode fracture envelope. Furthermore, Scanning Electron Microscopy (SEM) and X-ray micro-tomography were used to elucidate the mechanisms of surface failure and the morphology of internal damage.

© 2025 Elsevier LtdThis paper presents a semi-analytical Rayleigh–Ritz model for predicting the nonlinear aeroelastic behavior of skew-reinforced composite panels in supersonic flow until damage arises. The first-order shear deformation theory in conjunction with von Kármán strain nonlinearities is employed for the structural modeling, and quasi-steady first-order piston theory is used for aerodynamic loading. Direct time integration using the central difference method is employed to predict the full nonlinear dynamic response without resorting to modal reduction techniques. A comprehensive parametric study is conducted to assess the influence of various layups, skew angles, and stiffener configurations on the nonlinear aeroelastic response and damage detection. The results provide valuable insights into the flutter-induced damage in composite panels, aiding in the development of a preliminary tool for robust tolerance design. Furthermore, a novel strain energy-based assessment to determine the occurrence of Limit Cycle Oscillations is proposed.

© 2025 Elsevier LtdThis study addresses the solution of static, modal, buckling and aeroelastic analyses associated with rectangular plates based on the first-order shear deformation theory (FSDT), i.e., Reissner–Mindlin plates. For this purpose, a Modified Consistent Element-Free Galerkin (MCEFG) method was applied in combination with the moving least-squares (MLS) method for the obtainment of the admissible functions. Three improvements are implemented for the application of the MCEFG method: a new weighting function that diminishes the support radius influence in the MLS method, a stable and efficient numerical integration that guarantees the consistency of the method and an imposition of essential boundary conditions that do not require the augmentation of the weak form. Comparison studies on the displacement and generalized force fields, eigenfrequencies, buckling loads and flutter velocity are performed using numerical and theoretical results that confirm the accuracy and efficiency of the proposed methodology. Finally, the study considers four boundary conditions in order to guarantee the applicability of the method in different scenarios.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.Impact damage to composite structures results in multiple, complex failure modes, often requiring the replacement of entire components and thereby escalating aircraft maintenance costs. To address this issue, the present study investigates the damage propagation behaviour with particular emphasis on intra- and interlaminar failure modes. Carbon fibre/epoxy composites were subjected to tensile after impact (TAI) fatigue tests at different energy levels to induce different damage modes and extents within the specimens. A non-destructive testing technique (C-scan) was used to assess the interlaminar damage propagation, while the intralaminar fracture toughness of the post-impact specimens was characterised using a finite fracture mechanics model. The results show that the crack propagation behaviour is strongly influenced by the initial impact damage characteristics, in particular the impact energy level. Lower impact energies tend to promote interlaminar failure modes leading to fatigue crack propagation by delamination. Conversely, higher impact energy levels induce fibre fracture, resulting in a self-similar relationship between intra- and interlaminar propagation.

© 2025 Elsevier LtdAs an effort to reduce energy demand, researchers have been exploring the use of ejector pumps on cooling, heating and recirculation systems. To increase the ejectors efficiency, several studies propose optimizing the entrainment ratio and pressure ratio using CFD-based surrogate models. However, no study attempted to include an outlet temperature constraint, and there is no consensus on which surrogate model to use, or how to improve the models accuracy. The main goal of this paper is to develop a high-accuracy surrogate model, used to find optimal ejector geometries, that consider three functions of interest: maximizing the entrainment ratio, on various pressure ratios, constraining the outlet temperature. The methodology was implemented for a supersonic air ejector pump used to heat an aircrafts compartment. This work explore the correlation between the ejectors geometry and the functions of interest, the prediction accuracy of ten surrogate models, and a refinement process that increases the models accuracy at the pareto front. The resulting Universal Kriging model provided geometries that complied with the outlet temperature constraint and improved the entrainment ratio by 11.6% and 108.1% for the pressure ratios of 0.97 and 1.05, respectively, when compared to a geometry from the literature.

© 2025Ethanol-powered range-extended plug-in hybrid electric vehicles offer a sustainable alternative to reduce carbon emissions in light-duty transport. This study optimizes a BMW i3's range-extender engine for hydrous ethanol by increasing compression ratio, applying a Miller cycle, and using exhaust gas recirculation. Vehicle simulations and testing show a brake-specific fuel consumption reduction of up to 10.5 %, with a 4 % fuel efficiency gain over gasoline blends. Ethanol use decreased vehicle fuel consumption by over 20 % in most cycles and reduced overall energy consumption by 10 % compared to the gasoline range extender, though with a 5 % range loss due to ethanol's lower energy density. Despite this, ethanol's rapid refuelling capability presents an advantage over battery-electric vehicles. These findings highlight ethanol-powered range extenders as a practical solution to lower emissions while mitigating range anxiety.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.The global shift toward environmentally friendly renewable fuels is necessary to reduce dependence on fossil fuels and meet the climate goals established by competent international organizations. The aviation sector, a major GHG emitter, must reduce emissions to mitigate environmental impacts. In this context, the use of biojet fuels (or Sustainable Aviation Fuels, SAFs) as “drop-in” fuels has received great attention since it is considered the most efficient and fastest technique towards decarbonization. However, current technologies for converting biomass into biojet fuel have a high production cost and sales prices are not competitive with those of fossil jet fuel. Thus, this study evaluated the potential of an integrated system for biojet fuel production to satisfy the demand of the Brazilian market. The system was made up of four technologies: Alcohol-to-jet (ATJ), Fischer-Tropsch (FT), Syngas fermentation (SF), and direct sugar hydrocarbons (DSHC) using sugarcane as raw material, and jatropha fruit was also considered as raw material for the HEFA route. On the other hand, a techno-economic and environmental assessment was carried out to estimate the sales price of biojet fuel, the number of hectares to be used in biomass cultivation and the environmental impact generated in the production chain. The results demonstrated that an integrated system is a promising alternative for biojet fuel production generating an attractive sales price (1.09 US$ l−1) compared to individual conversion routes and a competitive sales price (0.55 US$ l−1) against fossil jet fuel. In addition, the use of hectares is reduced and environmental impacts are approximately similar to those generated by the individual conversion route as long as an adequate share (%) of a given route is chosen.

© 2025 Elsevier LtdA deeper understanding of the pyrolysis process for main and additional components in spent lithium-ion batteries (LIBs) could provide valuable insights for optimizing their recycling processes. This study examined the thermal behavior, kinetics, thermodynamics, and product evolution during the pyrolysis of laminate pouch primarily composed of polypropylene and polyamide. The kinetic compensation effect (KCE) and thermodynamic compensation effect (TCE) were also probed to provide a comprehensive understanding of the conversion. The degradation process was divided into three stages, with total mass loss ranging from 31.14 to 40.28 % and peak temperatures between 419 and 472 °C. The average activation energy was determined to be 118.06 kJ mol−1, with specific values of 99.25, 119.06 and 139.31 kJ mol−1 within conversion rate of 0.10–0.30, 0.35–0.75 and 0.80–0.95, respectively. The pouch conversion followed D1 diffusion mechanism. The KCE was confirmed and reconstructed fα=α0.45316(2α1.55)-1 displayed an excellent fit. Thermodynamic analysis implied that this conversion process was endothermic and non-spontaneous. Enthalpy and entropy relationship demonstrated the existence of TEC with compensation temperature (Tcomp) and experimental temperature (Texp) of 676.20 K and 693.23 K, respectively. In addition, free energy of compensation (ΔGcomp) was found to be 164.51 kJ mol−1, in agreement with experimental binding free energy (ΔGexp) range of 166.48–170.65 kJ mol−1, further confirmed the validity of the adopted mechanism.

© 2025 Elsevier LtdThermal treatment of spent lithium-ion batteries offers the benefits of decomposing organic components while concentrating valuable metals. This work investigated the kinetics, thermodynamics, and evolved products during the protection board pyrolysis under N2 and CO2 atmospheres. The degradation process was divided into stages of below 400 °C, 400–700 °C, and 700–900 °C. Peak temperatures at the maximum mass loss rate were observed at 359–399 °C in N₂ and 367–393 °C in CO₂. The primary products evolved from phenolics into ketones and acids, and eventually into alkanes. Brominated products such as bromomethane and 1-bromobutane were also detected, indicating the requirement of debromination to improve the usability of pyrolysis products. The average activation energies were determined to be 218.33 kJ/mol in N₂ and 308.91 kJ/mol in CO₂. D4 and D1 reaction mechanisms were found to best describe the pyrolysis process in two atmospheres. Positive values of ΔH and ΔG indicated the endothermic and non-spontaneous characteristics. The difference between ΔH and Ea values ranged from 5.26 to 7.70 kJ/mol in N₂ and 5.12–7.48 kJ/mol in CO₂, indicating a high possibility of overcoming the potential energy barrier.

© 2025 The Author(s). Propellants, Explosives, Pyrotechnics published by Wiley-VCH GmbH.Accurately evaluating accidental or intentional detonation scenarios is essential to ensure their intended effectiveness and/or protect personnel and structures. These evaluations often rely on estimating critical blast effect parameters through reference models, which adapt to different scenarios via key constants. The incident peak overpressure, the sudden pressure increase upon blast wave arrival, is a crucial parameter directly associated with wave-induced damage and demands precise calculation. An effective experimental approach involves tracking shock wave positions over time via calibrated high-speed footage. Processing these recordings and fitting parametric models to the data enables low-uncertainty peak overpressure estimation. This study presents a novel method utilizing constant trinitrotoluene (TNT) equivalence, a key parameter that quantifies the mass conversion of an explosive into its TNT equivalent on the basis of blast effects. The new model was compared with existing models in the literature in terms of peak overpressure and time of arrival estimation. These comparisons were made against direct measurements obtained from pressure sensors and high-speed recordings of open-air detonation tests involving center-initiated spherical Composition B explosions. The results indicate that the new model aligns more closely with experimental data than previously established models.

© 2025 IAAThe design of satellite attitude-control thrusters depends on a trade-off between minimum impulse bit and specific impulse, where the width of pulse maneuvers relies on the combination of delays in the hydraulic system (feed tubes and valves) and the ignition delay time of the propellant used. The most well-established propellants in this context are hydrazine derivatives and nitrogen tetroxide. However, their high toxicity makes satellite integration costly and environmentally hazardous. To replace these propellants, research is focused on developing new hypergolic green propellants, most of which use high-concentration hydrogen peroxide as an oxidizer. In this study, the hypergolic reaction between a blend of n-butanol and monoethanolamine and hydrogen peroxide was catalyzed using copper nitrate trihydrate. The central composite design method was applied to optimize fuel composition using 90% hydrogen peroxide as the oxidizer. The optimization yielded two key outcomes: for ignition delay time (31.5% n-butanol, 60% monoethanolamine, and 8.5% copper nitrate, resulting in an ignition delay time of 21.5 ms with a standard deviation of ±1.30 ms and a systematic error of ±0.4), and for theoretical specific impulse (36% n-butanol, 60% monoethanolamine, and 4% copper nitrate, with an ignition delay time of 26 ±0.4 ms). For the ignition delay time optimization, an oxidizer-fuel ratio of 4 was selected using CEA NASA software to achieve a maximum theoretical specific impulse of 170.64 s, while for specific impulse optimization, a ratio of 4.4 was chosen, resulting in a specific impulse of 171.58 s. Although the maximum theoretical specific impulse of the proposed green propellant pair does not present an advantage if compared to traditional hypergolic propellants, it offers a competitive advantage in terms of density-specific impulse, with the highest value achieved in the ignition delay time optimization, where the density-specific impulse of the system reached 267.5 gs/cm3. Furthermore, the addition of n-butanol effectively reduced fuel viscosity, enhanced density-specific impulse, increased specific impulse, and improved ignition delay time response with 90% hydrogen peroxide compared to pure monoethanolamine formulations for a specific chamber and nozzle configuration. These findings highlight the potential of this green propellant system to enhance performance and efficiency in aerospace applications.

© 2025 Elsevier LtdThe accelerated deployment of solar photovoltaic (PV) systems will inevitably result in an increasing volume of end-of-life PV panels, which will pose significant environmental challenges and could potentially hinder the growth of renewable energy systems. This study provided a comprehensive examination of the pyrolysis behavior, kinetics, thermodynamics, and evolved products of typical back sheet PVDF/PET/fluorine film (KPF). In addition, an analysis of the enthalpy-entropy compensation (EEC) was performed. Reactive force field molecular dynamics (ReaxFF-MD) simulations were employed to identify atomic-level intermediates and investigate the reaction pathway. The decomposition of KPF sample occurred in three stages, characterized by temperature ranges of below 473.15 K, 473.15–923.15 K, and 923.15–1173.15 K. The corresponding mass losses were found to be 0.61–0.90, 78.30–82.06, and 1.38–2.56 wt%, respectively. The predominant products identified included benzoic acid and its derivatives, which corroborated the strong presence of the C=O group in the FTIR analysis. ReaxFF-MD simulations revealed the formation of C7H4O2, C7H4O and C7H5O2 species, and the decomposition process was found to involve random scission, decarboxylation and decarbonylation reactions. Activation energies from the FWO, KAS, and Friedman methods exhibited a declining trend, decreasing from 72.12 to 40.92 kJ mol−1. The master-plot analysis indicated that the P2 mechanism provided a more accurate description of KPF pyrolysis. The positive ΔH and ΔG values confirmed that KPF decomposition was an endothermic and non-spontaneous process. The ΔH-ΔS relationship indicated the presence of an EEC, with a compensation temperature of 687.49 K and an experimental temperature of 766.60 K.

© 2025 Academia Brasileira de Ciencias. All rights reserved.The N5⁻ anion, known as pentazolate, represents a groundbreaking advancement in the field of energetic materials, offering promising applications in rocket propulsion, explosive devices, and pyrotechnics. Comprising five nitrogen atoms arranged in a cyclic structure with a negative charge, has captured significant interest due to its unique configuration and high energy potential. In this article, we provide a comprehensive overview of the N5⁻ anion’s potential as an energetic material, alongside the role of RMD simulations in elucidating its behavior. The ReaxFF forcefield was used to simulate the materials pyrolysis. The total energy behavior of different species containing pentazolate, across a range of temperatures (1500 K to 3000 K) revealed distinct trends and characteristics associated with the thermal dynamics and stability of the molecule under varying thermal conditions. Their mechanisms were elucidated, and the kinetic parameters were calculated, indicating that CNN5, with its low activation energy (39.14 kJ/mol), stands out as the most reactive, while PolyN5, with the highest activation energy (52.88 kJ/mol), is the most stable. Overall, the N5- anion represents a promising avenue for the development of high-energy materials.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The Professional Master Program in Aeronautical Engineering (MP-AER) is an initiative established in 2002 between ITA (Aeronautical Institute of Technology) and Embraer Industry to prepare new engineers for the development of new aircraft ventures. This Graduate Program has four phases. Phase 1 (first semester) offers courses in Fundamentals in Aeronautical Engineering. In Phase 2 (second semester) the student has to choose one career track and take several courses. In Phase 3 (third semester) all the students develop, in groups, the Capstone Aeronautical Project. In Phase 4, the student develops a Master’s Thesis. The purpose of this paper is to describe how the Capstone Project is organized and evaluated according to ABET criteria. The whole program description, the capstone project, and the continuous assessment and improvement processes are presented in detail. It is also shown how the Capstone Project prepares graduate students for a rapidly evolving work environment, which contributes to foster aeronautics in Brazil.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This study presents an experimental investigation of horn ice accretion on propeller performance. A small-scale propeller was designed with the aid of an analytical Blade-Element Momentum method, to operate within the wind tunnel envelope. Simulated horn ice shapes were applied to the blade surface, and the effects of horn geometry were assessed through a parametric variation of its main geometric features, such as height, surface position and radial distribution. Reynolds and Mach numbers effects on performance were also studied. Wind-tunnel tests revealed that ice shapes located at leading-edge to lower surface positions showed unexpected results presenting a greater thrust and comparable, or even lower, torque than the clean propeller. A leading-edge flap and an effective chord increase effects were identified as responsible for such outcomes. The ice shapes located on the upper surface caused the greatest performance degradation. The effects of ice surface position were observed to be directly proportional to the ice shape height. Both clean and iced configurations exhibited significant variation in performance coefficients with changes in rotational speed, attributed to the low reference Reynolds numbers associated to the small-scale tests and the limited rotation speeds imposed by the structural constraints of the resin printed propellers. Consequently, extrapolating these results to full-scale commercial propeller performance is not recommended.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This study aims to develop a computationally efficient numerical model to describe the vortex wake generated by a T-27 Tucano aircraft. The model is intended for future integration into the Variable Stability Simulator at the Flight Test and Research Institute (IPEV) and the training simulators at the Brazilian Air Force Academy (AFA). These applications seek to include a realistic aerodynamic model to improve the fidelity of formation flight simulations, contributing to the enhancement of training techniques and operational safety for both flight test pilots and cadets of the Brazilian Air Force (FAB). The algorithms were developed by integrating the circulation distribution results obtained from potential flow calculations using the panel method applied to an aircraft model into a Vortex Filament Method (VFM). This approach was adapted with the Burnham-Hallock (B-H) vortex model and combined with propulsion results derived from Goldstein and Theodorsen’s helical vortex sheet model for propellers. The integration enabled the generation of a complete velocity field at any point in space, allowing not only the calculation of the wake produced by a large formation of aircraft but also the downstream spatial evolution of the wake in a non-stationary model.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This study investigates the aerodynamic interaction between propellers and wings using VSPAERO. The research evaluates the tool’s capability to predict aero-propulsive effects through hisolated and integrated analyses of two reference geometric models: a Conventional Model (CM)and a Wingtip-Mounted Model (WMM). Results for the isolated wing show good agreement with experimental data, particularly for lift coefficients, with acceptable deviations for drag coefficients. For the isolated propeller, VSPAERO demonstrated consistency in predicting thrust coefficients, although power coefficients were overestimated. Integrated analyses highlighted challenges in modeling complex configurations, such as discrepancies in aerodynamic coefficients requiring adjustments to solver parameters. A parametric study examining the influence of propeller positioning relative to the wing was also conducted, showing significant effects on aero dynamic efficiency and propeller performance. The findings indicate that VSPAERO is a promising tool for conceptual design and preliminary studies of propeller-wing interactions, with further validation needed for more complex configurations.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This study presents a numerical investigation on the effects of horn ice accretion on propeller performance, with a focus on how the position of the ice shape on the leading-edge surface affects performance. Using the RANS CFD code OpenFOAM, numerical simulations were performed on the same configurations previously tested by the author in a wind tunnel. The numerical analysis aimed to clarify and support interpretation of some unexpected wind-tunnel results, where certain icing configurations demonstrated higher thrust and lower torque compared to the clean configuration. A mesh independence study identified an optimal balance between computational efficiency and result consistency, leading to a mesh that could accurately captured performance trends observed in the wind tunnel. Numerical results for ice position effects showed strong alignment with experimental data, especially for thrust coefficients, while torque coefficient trends matched well despite an offset in absolute values. The CFD simulations reliably represented the differences between clean and iced configurations, even with a simplified mesh. Although RANS models have known limitations in predicting highly separated flows, essential to understanding icing impacts, the CFD analysis contributed with valuable insights on pressure distributions and flow topology. These additional data were fundamental in interpreting and validating the wind-tunnel findings, advancing the understanding of icing effects on propeller aerodynamics.

© 2025 by Geovana Neves.This paper introduces the Standard Model ITA (SMI), an interchangeable aircraft model framework designed to investigate aeropropulsive integration of propellers in support of future sustainable aviation applications. Early design phases progress rapidly, requiring streamlined methods to capture aeropropulsive effects from high-level parameters within product development time constraints. Designed as a generic approach, the methodology can integrate aerodynamic data from theoretical models and wind tunnel tests (WTT), leveraging information at the integrated coefficient level to support quick comparative analysis. The method focuses on longitudinal characterization, describing the local angle of attack and dynamic pressure at the horizontal tail using 3D-equivalent parameters. For rear-mounted configurations, the same procedure enables the calculation of averaged propeller slipstream swirl and dynamic pressure effects at the pylon, while installed propeller inflow angles are determined via in-plane force analysis. The aerodynamic evaluation of the SMI platform was carried out using CFD RANS simulations for power-off conditions, with further characterization in poweron conditions using Flightstream®, a panel method solver. The wing-mounted configuration (SMI-L1) exhibits a significant reduction in static stability in powered conditions, whereas rear-mounted configurations (SMI-L2 and SMI-L3) are inherently more stable concepts. This research provides a structured methodology for incorporating aeropropulsive effects early in the design cycle, enhancing aircraft sizing efforts and supporting sustainable aviation objectives.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Although the measurement of pilot’s effort during flight tasks can use a great amount of different technologies, including robust instrumentation and many qualitative rating scales, until nowadays the pilot’s subjective opinion has great importance in the final decision. During an Air to Air Refueling certification process, where many flight hours was spent and the cost efficiency is of utmost importance, data analysis indicates that pilot workload can be assessed both through subjective scales and the measurement of command displacements. Many issues must be taken into consideration when measuring pilot effort using Helicopter Air-to-Air Refueling: the long flights, sometimes for more than six hours, can influence the pilot’s judgment, and the lack of power margin between both aircraft can influence the actions on commands. A quantitative methodology using the command displacements named P95 was defined and described in the paper published at the AIAA SciTech Conference 2024[1], and some details are reviewed in the present work. As an improvement of the P95 methodology, in this article it was applied to other vehicles, helicopters and fixed-wing aircraft performing different tasks, and an analysis of pilot workload was carried out and compared with qualitative degrees of workload. To validate this technique, the trials were done firstly in an engineering flight simulator and after, in real flights. The main objective of this work is to analyze the applicability of the P95 methodology in different aircraft, providing an additional tool to subjective evaluations to identify the workload in flight.

© 2025 Author(s).The present work explores a bio-inspired modification of a cylinder, incorporating a wavy pattern inspired by humpback whale flipper tubercles. Drawing on prior research on airfoils and wings, the investigation provides valuable insights into the implications of this novel geometry on cylinder flow, contributing to the existing knowledge in the field. A selection of four patterns of waviness (varying in amplitudes and wavelengths) is compared to a smooth (i.e., straight cylinder) model by measuring pressure distribution and aerodynamic forces. The study is conducted in a wind tunnel, considering Reynolds numbers from about 3.9 × 10 4 to 1.9 × 10 5 . Notable findings include a drag coefficient reduction of up to 25% for a model with 12% wavelength and 3% waviness amplitude. Flow visualization reveals the presence of two distinct phenomena: the formation of three-dimensional laminar separation bubbles, and the indications of counter-rotating vortex pairs over the cylinder surface. These flow structures contribute to explain the observed drag variation through changes in the separation line, base pressure, and other associated mechanisms. This study enhances our understanding of the performance of such bio-inspired designs.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Adaptive refinement methods can help speed up expensive simulations by reducing the amount of user-dependent processes during mesh generation. One of the most crucial steps in these methods is identifying regions requiring spatial resolution interventions. One of the most straightforward ways of doing this is using featured-based indicators. Because of their general simplistic nature, they may be inefficient in detecting problematic elements under specific numerical circumstances. The current work seeks to analyze these indicators in the context of spectral/hp discretization using continuous Galerkin. We categorized the indicators into three groups: jump, spectral, and error-based. The first two had their performance tested, while the last was employed as a reference. We analyzed them using multiple one-dimensional and one two-dimensional tests to verify how different feature-based indicators perform in distinct numerical circumstances. To measure their performance, we analyze their capability to decrease discretization error when guiding a sequence of p-adaptation cycles. The indicator that performed most consistently well was based on the maximum derivative jump.

© 2024Identifying the occurrence of gear contact fatigue failure as early as possible is essential for condition-based maintenance (CBM). Vibration signals can be used to identify gear contact fatigue. However, the use of vibration signals can be challenging due to its complexity, compounded by lower levels of vibration during the initial stages of contact fatigue. The present study details a new algorithm that integrates stand-alone features to correlate the vibrational signal with early failure occurrence. The study aim is to identify the failure in the early stages, before reaching the ISO 6336–5 stopping criterion of 4 % damaged area. A damage induction on the flank of helical gears is applied to simulate and characterize the failure occurrence. Damping characteristics with impact evaluation, Kurtosis analysis and the monitoring of the Gear Meshing Frequency are applied to characterize the failure signature. This strategy stands out by the integration of these stand-alone features and their behavior. The algorithm's capacity is verified through durability tests, promoting the natural evolution of this failure mode. Results show a success rate of above 80 % at identifying the failure presence before the stopping criterion limit.

© 2025 by the authors.Molybdenum disulfide is a 2D material with excellent lubricant properties, resulting from weak van der Waals forces between lattice layers and shear-induced crystal orientation. The low forces needed to shear the MoS2 crystal layers grant the tribological system low coefficients of friction (COF). However, film oxidation harms its efficacy in humid atmospheres, leading to an increased COF and poor surface adhesion, making its use preferable in dry or vacuum conditions. To overcome these challenges, doping MoS2 with elements such as Nb, Ti, C, and N emerges as a promising solution. Nevertheless, the adhesion of these coatings to a steel substrate presents challenges and strategies involving the reduction in residual stresses and increased chemical affinity to the substrate by using niobium-based materials as interlayers. In this study, Nb-doped MoS2 films were deposited on H13 steel and silicon wafers using the pulsed direct current balanced magnetron sputtering technique. Different niobium-based interlayers (pure Nb and NbN) were deposited to evaluate the adhesion properties of Nb-doped MoS2 coatings. Unlubricated scratch tests, conducted at room temperature and relative humidity under a progressive load, were performed to analyze the COF and adhesion of the coating. Instrumented indentation tests were conducted to assess the hardness and elastic modulus of the coatings. The microstructure of the coatings was obtained by Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Transmission Electron Microscopy (TEM), with Energy-Dispersive X-Ray Spectroscopy (EDS). Results indicated that niobium doping on MoS2 coatings changes the structure from crystalline to amorphous. Additionally, the Nb concentration of the Nb:MoS2 coating changed the mechanical properties, leading to different cohesive failures by different loads during the scratch tests. Results have also indicated that an NbN interlayer optimally promoted the adhesion of the film. This result is justified by the increase in hardness led by higher Nb concentrations, enhancing the load-bearing capacity of the coating. It is concluded that niobium-based materials can be used to enhance the adhesion properties of Nb-doped MoS2 films and improve their tribological performance.

© 2024 Informa UK Limited, trading as Taylor & Francis Group.Additive manufacturing (AM) is a rapid prototyping technology that offers many advantages over conventional manufacturing processes. However, to make the most of the AM advantages, some requirements need to be met, such as the adjustment of process parameters and quality of the feedstock. This work assessed the influence of carrier gas flow rate and particle size of AISI M2 in the laser-directed energy deposition process (L-DED). Different carrier gas flow rates were tested for two powders with particle size of 53–150 µm (larger range) and 20–53 µm (lower range). The variation of carrier gas flow rate and particle size was assessed in single lines and layers. The results show that increasing the carrier gas flow rate provides better powder convergence in the region where there is interaction with the laser beam and faster particle velocity. The lower range tends to have greater efficiency in the deposition of single lines and layers. Regarding geometric characteristics, the aspect ratio did not show a well-defined trend as a function of the carrier gas flow rate and particle size, however, the layer height tends to be greater for the lower range, while the dilution tends to be greater for the larger range.

© ASM International 2025.Energy transition has brought tighter requirements to high-performance gears, especially the demand for increased power density. Usually applied after grinding, isotropic superfinishing stands for a solution to reduce flank roughness and consequently the contact stresses. The objective of this study is comprehending how the residual stresses induced by the grinding process influence the superfinished surface integrity. Specimens were pointedly ground to induce distinct residual stress states in terms of maximum intensity, surface heterogeneity, and in-depth profile. They were then subjected to isotropic superfinishing in a single condition. The investigation showed that, after the isotropic superfinishing, the ground residual stress state is preserved. The results of both intensity and heterogeneity of residual stresses demonstrate that the superfinished surface is strongly influenced by the previous manufacturing stage, to which the proposed mechanism of interaction is verified.

© 2025 COSPARThis work describes the development of a semi-analytic theory for a preliminary orbit analysis of the GARATÉA-L Brazilian lunar probe. The dynamical model includes the effects of the zonal harmonics J2 up to J12, the effects of second- and third-degree tesserals and sectorials, and the third-body perturbation due to the attraction of the Earth. The Hamiltonian describing the dynamics is implicitly expressed in Delaunay variables, and, Hori's method is applied to derive a semi-analytic solution which is expressed in closed form with respect to the eccentricity. Expressions for Keplerian orbital elements are obtained including short-period and medium-period terms. In order to avoid singularities in eccentricity, non-singular orbital elements are introduced to compute frozen orbit conditions considering several values of inclinations and semi-major axes. A preliminary analysis of the orbit of the GARATÉA-L Brazilian probe is conducted, and the results are compared to those provided by several models using Cowell's method. A realistic model based on ephemeris data is also used for comparison. The findings reveal that the probe's nominal orbit does not exhibit a frozen condition in terms of eccentricity. A new inclination is proposed to freeze the orbit without altering the pericenter and apocenter altitudes. However, orbital evolution results in a collision with the Moon, as revealed by the 50 × 50 models. A polar frozen orbit is then suggested, offering the advantage of gradually shifting the sub-pericenter point from the South Pole toward the center of the Aitken Basin region.

© 2025 Elsevier B.V.Periodic structures have attracted interest across various fields of science and engineering due to their unique ability to manipulate wave propagation. The Wave-based Finite Element Method (WFEM) is typically employed to model such systems by relying on the dynamic behavior of a single unit cell of the lattice. However, the WFEM can face challenges in handling unit cell finite element (FE) models with several degrees of freedom (DoFs), as it involves operating with large-sized matrices. Therefore, in this work, we combine the WFEM with the Generalized Bloch-Mode Synthesis (GBMS) to offer a highly efficient and accurate method for modeling periodic structures. Three different types of unit cells were investigated in this study, demonstrating that highly reduced unit cell models can be obtained using the Craig-Bampton (CB) and Local-level Characteristic Constraint (L-CC) model reduction methods. By leveraging the advantages of the WFEM and the reduced-order unit cell models, harmonic forced responses were rapidly and accurately computed. Additionally, we showed that combining the WFEM with the GBMS mitigates numerical issues when computing forced responses, as the boundary DoFs are reduced to a smaller number of equations, avoiding the computation of high-order evanescent modes, a task that can be difficult to perform accurately for some unit cells.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.This work investigates a novel metamaterial concept using the Wave-based Finite Element Method. The metamaterial comprises a periodic-like structure manufactured through fused filament deposition, featuring internal cavities filled with water. Experimental characterization of the dynamics of the periodic system without internal fluid confirms good agreement with numerical predictions obtained through frequency response function measurements. Furthermore, the dynamic behavior of the two-phase periodic metastructure is experimentally examined, where waves interact within the heterogeneous medium consisting of both fluid and solid phases. In this case, the resulting wave characteristics depend on the properties of both phases. It was shown that the fluid-filled metastructure exhibits vibration reduction through the whole frequency range compared to the case lacking internal fluid. Additionally, it was seen that the frequency range near the second attenuation band of the periodic metastructure without fluid can be enlarged after the fluid inclusion within the cavities of its unit cells, as a consequence of mass increase and damping effects. Consequently, this work presents a promising avenue for metastructure design, with potential applications in structural dynamics and acoustics.

© 2024Periodic structures have been attracting a great deal of academic and industrial interest lately, due to their distinctive vibration and wave propagation behavior, which can be explored for the development of innovative solutions to structural dynamics and vibroacoustic problems. Although such a potential has been demonstrated in a large number of studies, the investigation of detrimental effects, which can be present in practical applications, is still necessary. This paper reports investigations on the combined influence of uncertainties affecting ambient temperature — which alters material properties and induces stress-stiffening due to constrained thermal dilatation — and boundary conditions (BCs) on the bandgap characteristics of periodic beams. The space-dependent temperature fluctuations are represented as a one-dimensional stationary Gaussian random field, discretized using the Karhunen-Loève expansion, while non-ideal BCs, represented as springs, are modeled as discrete random variables. Sampling-based stochastic analyses of the central frequency and bandwidth of the beam's attenuation bands are performed using Monte Carlo simulations. The results demonstrate that the variability in the attenuation band features is influenced not only by the coefficients of variation (CVs) of the input random quantities, but also by the correlation length of the random temperature fluctuations. Numerical simulations reveal that the bandgap central frequency is primarily affected by the temperature random field, while the BCs govern the bandwidth. Although low CV and standard deviation values are obtained for the dispersion of the bandgap features, reliability analyses indicate that some designs exhibit low reliability. Increased variability in both the bandgap central frequency and bandwidth is observed for greater temperature correlation lengths and CVs. The contributions of the study include the proposal of a comprehensive stochastic modeling procedure duly accounting for relevant random influences, and evidencing that those influences can be significant, requiring consideration in the design of robust periodic structures.

© The Author(s), 2025. Published by Cambridge University Press. This is an Open Access article,In a combined experimental and numerical effort, we investigate the generation and reduction of airfoil tonal noise. The means of noise control are streak generators in the form of cylindrical roughness elements. These elements are placed periodically along the span of the airfoil at the mid-chord streamwise position. Experiments are performed for a wide range of Reynolds numbers and angles of attack in a companion work (Alva et al., AIAA Aviation Forum, 2023). In the present work, we concentrate on numerical investigations for a further investigation of selected cases. We have performed wall-resolved large-eddy simulations for a NACA 0012 airfoil at zero angle of attack and Mach 0.3. Two Reynolds numbers (0.8 × 105 and 1.0 × 105) have been investigated, showing acoustic results consistent with experiments at the same Reynolds but lower Mach numbers. Roughness elements attenuate tones in the acoustic field and, for the higher Reynolds number, suppress them. Through Fourier decomposition and spectral proper orthogonal decomposition analysis of streamwise velocity data, dominating structures have been identified. Further, the coupling between the structures generated by the surface roughness and the instability modes (Kelvin–Helmholtz) of the shear layer has been identified through stability analysis, suggesting stabilisation mechanisms by which the sound generation by the airfoil is reduced by the roughness elements.

© 2025 Author(s).The present work explores a bio-inspired modification of a cylinder, incorporating a wavy pattern inspired by humpback whale flipper tubercles. Drawing on prior research on airfoils and wings, the investigation provides valuable insights into the implications of this novel geometry on cylinder flow, contributing to the existing knowledge in the field. A selection of four patterns of waviness (varying in amplitudes and wavelengths) is compared to a smooth (i.e., straight cylinder) model by measuring pressure distribution and aerodynamic forces. The study is conducted in a wind tunnel, considering Reynolds numbers from about 3.9 × 10 4 to 1.9 × 10 5 . Notable findings include a drag coefficient reduction of up to 25% for a model with 12% wavelength and 3% waviness amplitude. Flow visualization reveals the presence of two distinct phenomena: the formation of three-dimensional laminar separation bubbles, and the indications of counter-rotating vortex pairs over the cylinder surface. These flow structures contribute to explain the observed drag variation through changes in the separation line, base pressure, and other associated mechanisms. This study enhances our understanding of the performance of such bio-inspired designs.

© 2025 by Geovana Neves.This paper introduces the Standard Model ITA (SMI), an interchangeable aircraft model framework designed to investigate aeropropulsive integration of propellers in support of future sustainable aviation applications. Early design phases progress rapidly, requiring streamlined methods to capture aeropropulsive effects from high-level parameters within product development time constraints. Designed as a generic approach, the methodology can integrate aerodynamic data from theoretical models and wind tunnel tests (WTT), leveraging information at the integrated coefficient level to support quick comparative analysis. The method focuses on longitudinal characterization, describing the local angle of attack and dynamic pressure at the horizontal tail using 3D-equivalent parameters. For rear-mounted configurations, the same procedure enables the calculation of averaged propeller slipstream swirl and dynamic pressure effects at the pylon, while installed propeller inflow angles are determined via in-plane force analysis. The aerodynamic evaluation of the SMI platform was carried out using CFD RANS simulations for power-off conditions, with further characterization in poweron conditions using Flightstream®, a panel method solver. The wing-mounted configuration (SMI-L1) exhibits a significant reduction in static stability in powered conditions, whereas rear-mounted configurations (SMI-L2 and SMI-L3) are inherently more stable concepts. This research provides a structured methodology for incorporating aeropropulsive effects early in the design cycle, enhancing aircraft sizing efforts and supporting sustainable aviation objectives.

© 2025 Elsevier LtdAs an effort to reduce energy demand, researchers have been exploring the use of ejector pumps on cooling, heating and recirculation systems. To increase the ejectors efficiency, several studies propose optimizing the entrainment ratio and pressure ratio using CFD-based surrogate models. However, no study attempted to include an outlet temperature constraint, and there is no consensus on which surrogate model to use, or how to improve the models accuracy. The main goal of this paper is to develop a high-accuracy surrogate model, used to find optimal ejector geometries, that consider three functions of interest: maximizing the entrainment ratio, on various pressure ratios, constraining the outlet temperature. The methodology was implemented for a supersonic air ejector pump used to heat an aircrafts compartment. This work explore the correlation between the ejectors geometry and the functions of interest, the prediction accuracy of ten surrogate models, and a refinement process that increases the models accuracy at the pareto front. The resulting Universal Kriging model provided geometries that complied with the outlet temperature constraint and improved the entrainment ratio by 11.6% and 108.1% for the pressure ratios of 0.97 and 1.05, respectively, when compared to a geometry from the literature.

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2025.The aircraft flying qualities are assessed during preliminary design phases through dynamic stability derivatives and an adequate accuracy is necessary to avoid costly fixes after flight testing. The dynamic stability derivatives estimation process uses unsteady CFD or dynamic data acquisition in wind tunnel testing, but both are very expensive. However, using the Navier–Stokes equations rewritten in non-inertial reference frame embedded in a CFD software it is possible to estimate dynamic aerodynamic coefficients using steady-state CFD, which is demonstrated in the present work with adequate accuracy for both 2D and 3D study cases.

© The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2025.Optimizing the energy conversion processes within aircraft and developing novel aircraft configurations have become imperative for fostering a more sustainable aviation sector. Exergy analysis emerges as a valuable tool in pinpointing areas for improvement and evaluating innovative configurations. The present work intends to expand upon the exergy concept in the assessment of airfoil aerodynamics. This is achieved through drag breakdown and flow field analysis utilizing the exergetic method. The study employs computational fluid dynamics analysis, utilizing the airfoil NACA 0012 for subsonic compressible flow and NACA 2315, NACA 2312, and NACA 2309 for transonic compressible flow as test cases to illustrate the concept. Rates of exergy destruction and a thorough flow field analysis are presented along the wake downstream of the airfoil, comparing four turbulence models. The theoretical exergy method is juxtaposed with the classical near-field method and validated through technical reports. Ultimately, the findings indicate a potential for improvement using the exergy method in aerodynamics, resulting in a 12% reduction in drag in a 2D flow field, translating into potential energy savings up to 31000 W. Furthermore, it is also demonstrated that the impact of airfoil thickness variation on exergy destruction in the transonic regime is found to be negligible.

© 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This paper showcases the collaborative efforts between ITA (academic) and Embraer (aircraft manufacturer) in developing advanced methods to address the upcoming challenges of the 4th Aeroelastic Prediction Workshop. For predicting static wing loads, a rapid conceptual design method that accounts for structural geometric nonlinearity is introduced. A matched flutter solution is proposed for control surface flutter in geometrically nonlinear wings. For predicting limit cycle oscillations, the approach combining an unsteady vortex lattice with a transient structural geometric nonlinear solver is presented. Furthermore, a framework that integrates an open-source Reynolds-Averaged Navier-Stokes solver with a geometric nonlinear structural solver is developed to handle transonic static deflections.

© 2025 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The Actuator Line Method (ALM) is a technique that replaces the detailed airfoil geometry with distributed body forces to predict the flow field. ALM has been widely employed for simulating rotating blade wakes due to its flexibility and accuracy in the far field. In this study, the applicability of ALM for unsteady aerodynamics and acoustic field prediction is evaluated. The case study considered is the harmonic transverse oscillation of a thin airfoil in uniform flow. The ALM body forces are distributed over a few grid points following a Gaussian function, with a range of smearing ratio of ε/c (smearing parameter over the chord length) between 0.4 and 1. These forces are computed using thin airfoil theory with the Prandtl-Glauert correction for compressible regime. Based on these computations, the compressible Navier-Stokes equations are numerically solved, yielding the velocity and pressure fields. ALM lift results are validated against unsteady aerodynamic theory in the subsonic regime. Moreover, results demonstrate an acoustic field consistent with a dipole distribution and a spectrum exhibiting a frequency corresponding to the plunging motion. Furthermore, the acoustic results are validated through an acoustic analogy approach, involving the prediction of the acoustic field via Green’s function. The prediction of the acoustic far-field using ALM is expected to significantly reduce the computational cost of compressible simulations applied to propeller and wind turbine aeroacoustics.

© 2024 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The capacity to keep a desired topology with a requested accuracy plays a significant role in every spacecraft formation-flying operation. These missions can be terminated in case of an unexpected spacecraft fault, preventing the system from returning to its nominal configuration. This paper presents and tests a new recovery solution, called Reconfigurable Guidance Strategy (RGS), for the spacecraft formation-flying control problem subject to a look-inplace permanent thruster fault. The proposed method relies on autonomously and in real-time reconfiguring the guidance function to compensate for the loss of the spacecraft actuation system. The performance and cost of the RGS have been tested in a high-fidelity simulation scenario, the 42 spacecraft simulator developed by NASA Goddard Space Flight Center, taking into account orbital and rotational nonlinear coupled dynamics, high-order perturbation models, and actuator and sensor models. The numerical simulation results have demonstrated the proposed recovery strategy’s effectiveness, feasibility, and robustness.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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