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AIAA Science and technology Forum and Exposition, AIAA SciTech Forum 2025

作者： Hatashita, Luis H. Jain, Suhas S. Daniel Guggenheim School of Aerospace Engineering Flow Physics and Computational Science Lab Georgia Institute of Technology 270 Ferst Drive NW Atlanta30332 Georgia George W. Woodruff School of Mechanical Engineering Flow Physics and Computational Science Lab Georgia Institute of Technology 801 Ferst Drive NW Atlanta30332 Georgia

ISBN: (数字)9781624107238

ISBN: (纸本)9781624107238

Classical diffuse interface methods for non-equilibrium formulations of two-phase flows are not capable of preserving interface-thickness. Furthermore, when coupled with shockcapturing schemes, the interface may diffuse in its entirety. Thus, it is of utmost importance for accurate simulation of two-phase flows to describe interface-preserving formulations. Herein, a conservative interface-regularization formulation based on the phase-field method is proposed, and it analytically guarantees boundedness of volume fraction, absence of spurious oscillations of phasic kinetic energy and mixture entropy preservation in the absence of relaxation. The formulation is shown to stabilize dispersion errors originated due to the interface jumps and to preserve interface thickness when discretized with low lost and low dissipation second-order schemes. A possible issue with this formulation and discretization is the possibility of failing to preserve positivity of quantities of interests, hence, a blending strategy with a Lax-Friedrichs flux is also proposed and tested. In highly compressible scenarios such as shock-drop interaction, the interface regularization when applied to the positive-preserving flux is demonstrated to improve qualitative results on coarser grids. © 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Kinetic energy

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Effects of phase synchronization on the tonal sound directivity of distributed propellersa)

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Journal of the Acoustical Society of America 2025年第5期157卷 3267-3281页

作者： Zarri, A. Prenter, F. de Avallone, F. Ragni, D. Casalino, D. Department of Flow Physics and Technology Delft University of Technology Kluyverweg 1 Delft2629 HS Netherlands Aeronautics and Aerospace Department von Karman Institute for Fluid Dynamics Waterloosesteenweg 72 Sint-Genesius-RodeB-1640 Belgium Department of Mechanical and Aerospace Engineering Politecnico di Torino Torino10129 Italy

Recent studies on distributed electric propulsion systems suggest phase synchronization between rotors as a noise reduction strategy. However, the aerodynamic interactions between propellers' near fields and their influence on far-field tonal noise remain poorly understood, partly due to experimental limitations in microphone placement. This paper addresses this gap through lattice Boltzmann very large eddy simulations of three adjacent, co-rotating rotors, spaced radially at 2% of their diameter, to investigate how relative phase angle affects tonal noise directivity. Results reveal that proximity-induced aerodynamic interactions generate dominant tonal noise in most spatial directions, driven by two mechanisms: time-averaged inflow distortion from nearby propellers and impulsive local effects at blade tips, with the latter influenced by phase angle. While the directivity pattern of the blade-passing frequency harmonic tone remains consistent across phase angles, comparing cases with zero relative phase (blades aligned) and opposite-phase conditions shows sound pressure level shifts of up to 4.5 dB along the primary noise axis, namely, along the inflow direction. Conversely, acoustic interference significantly alters noise directivity, especially in opposite-phase conditions where sound is nearly canceled in specific directions. These findings highlight rotor synchronization as a promising strategy for reducing noise emissions toward sensitive areas. © 2025 Author(s).

关键词： Noise abatement

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Twist- and cross-phase-modulated Laguerre-Gaussian correlated Schell-model beam and its radiation forces

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Optics Express 2025年第3期33卷 4803-4816页

作者： Peng, Xiaofeng Zhu, Yuguang Liu, Lin Wang, Haiyun Liu, Leixin Cai, Yangjian Shandong Provincial Engineering and Technical Center of Light Manipulations Shandong Provincial Key Laboratory of Optics and Photonic Device School of Physics and Electronics Shandong Normal University Jinan250014 China Collaborative Innovation Center of Light Manipulation and Applications Shandong Normal University Jinan250358 China School of Physical Science and Technology Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou215006 China Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application School of Physical Science and Technology Suzhou University of Science and Technology Suzhou215009 China

In this paper, we introduce what we believe to be a novel partially coherent beam with a nonconventional correlation function, named the twist- and cross-phase-modulated Laguerre-Gaussian correlated Schell-model (TCPM-LGSM) beam, which carries both twist and cross phase. The propagation properties of the TCPM-LGSM beam have been investigated in detail. Our results indicate that both the twist phase and cross phase hinder the evolution of the beam’s intensity distribution from a Gaussian to a hollow profile due to the correlation structure. Additionally, when the beam simultaneously carries both phases, it forms an intensity distribution with two intensity peaks in the focal plane. Furthermore, the twist phase and cross phase can improve the beam’s ability to maintain its distribution of the spectral degree of coherence (SDOC) in the far field. Under the combined influence of phases, although the distribution of the SDOC changes, it significantly enhances the ability to measure the order of the correlation structures with higher orders. Moreover, we studied the orbital angular momentum (OAM) distribution of the TCPM-LGSM beam and found that, although the correlation structure itself does not carry OAM, it substantially alters the beam’s OAM distribution when beam carries the twist and cross phase. Finally, we explored the application of the proposed beam in particle trapping. By modulating the beam’s source parameters, particles can be trapped at the ring, the center, or at the two intensity peaks, respectively. This work provides valuable theoretical guidance for information transfer and particle trapping. © 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

关键词： Gaussian distribution

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Promoting Mn3+ Spin-State Transitions from t2g to eg through Ni Doping in Antiperovskite CuNMn3 for Highly Efficient Ammonia Synthesis

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Journal of Physical Chemistry Letters 2025年第20期16卷 5025-5033页

作者： Yan, Yuxiang Zhou, Jinyu Ren, Hengdong Li, Linze Wang, Ka Feng, Lei Ma, Siying Wu, Qifan Wang, Di Yang, Yurong Ma, Chunlan Xu, Xiaobing Wu, Xinglong National Laboratory of Solid States Microstructures and School of Physics Nanjing University Nanjing210093 China National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering Nanjing University Nanjing210093 China Jiangsu Key Laboratory of Artificial Functional Materials Nanjing University Nanjing210093 China Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application School of Physical Science and Technology Suzhou University of Science and Technology Suzhou215009 China College of Electronic Engineering Nanjing Xiaozhuang University Nanjing211171 China

The electrochemical nitrogen reduction reaction (e-NRR) offers a sustainable approach to ammonia synthesis under ambient conditions, with the potential to replace the energy-intensive Haber-Bosch process. Despite significant progress in this promising field, the low NH3 yield rate and limited Faradaic efficiency (FE) remain formidable challenges. Here, we introduce antiperovskite Cu1-xNixNMn3, where partial substitution of Cu by Ni in CuNMn3 is developed as an effective and robust e-NRR electrocatalyst. Notably, Cu0.7Ni0.3NMn3 demonstrates outstanding e-NRR performance, achieving an NH3 yield rate of 33.9 ± 1.1 μg h-1 mg-1, an FE of 19.2 ± 0.62% at −0.4 V versus RHE, and excellent long-term stability over 50 h of electrolysis. In-depth mechanistic studies reveal that the Ni/Cu exchange process in Cu1-xNixNMn3 maintains structural integrity and stabilizes the valence states. Ni atoms at the corner sites interact with adjacent Mn atoms at the face centers via antiferromagnetic interactions, altering the original magnetic exchange interactions. This modification triggers a spin-state transition of some Mn3+ ions from a low-spin (t2g4eg0) to a high-spin (t2g3eg1) configuration. Density functional theory (DFT) calculations confirm that the improved eg orbital electronic configuration enhances N2 adsorption energy at Mn catalytic sites and promotes the hydrogenation of N2 to form *NNH intermediates, thereby accounting for the high activity of Cu0.3Ni0.7NMn3 in the e-NRR. © 2025 American Chemical Society.

关键词： Electrolytic reduction

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Streaky perturbations in swept-wing flow over forward-facing step

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Physical Review Fluids 2025年第2期10卷 023902-023902页

作者： Jordi Casacuberta Sven Westerbeek Juan Alberto Franco Koen J. Groot Stefan Hickel Stefan Hein Marios Kotsonis Department of Flow Physics and Technology Faculty of Aerospace Engineering Delft University of Technology Kluyverweg 1 2629HS Delft The Netherlands Institute of Aerodynamics and Flow Technology German Aerospace Center Bunsenstrasse 10 37073 Göttingen Germany Universidad Politécnica de Madrid Plaza Cardenal Cisneros 3 E-28040 Madrid Spain Department of Mechanical Engineering University of Wyoming Laramie Wyoming 82072 USA

Stationary velocity-perturbation streaks have recently been identified in laminar swept-wing boundary-layer flow interacting with a surface forward-facing step. Streaky structures at the step promote early laminar-turbulent transition under certain conditions. This work utilizes direct numerical simulations to explore the mechanisms of growth of stationary streaks at the step and provides insight into their origin, nature, and spatial organization. The analysis is mainly focused on, but not restricted to, incoming perturbations in the form of stationary crossflow instability. Stationary streaky structures are found to be universal to swept forward-facing-step flow subjected to three-dimensional perturbations in the incoming boundary layer. The streaks at the step are primarily ascribed to the lift-up effect. They appear as a linear perturbation response of the highly sheared step flow to the cross-stream pattern of incoming perturbations. A mechanism of base-flow deceleration additionally contributes to feeding growth to the streaks. Linear stability analysis carried out through the harmonic Navier-Stokes method confirms that the streaks are a linear perturbation phenomenon. Effects of spanwise perturbation wavelength and effective sweep angle on the mechanisms of the streaks are also assessed.

关键词： Swept wings

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Accurate calculation of bubble and droplet properties in diffuse-interface two-phase simulations

arXiv

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arXiv 2025年

作者： Nathan, Pranav J. Jain, Suhas S. Flow Physics and Computational Science Lab George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology AtlantaGA United States

In this paper, we address the challenge of accurately calculating droplet/bubble properties (e.g., volume, number) in diffuse-interface two-phase flow simulations. Currently, flood-fill algorithms can truncate a significant portion of the volume of droplets/bubbles contained within the diffuse interface region or artificially merge multiple droplets/bubbles. This error is also dependent on the volume fraction cutoff value, which is typically chosen to be 0.5 arbitrarily, in the flood-fill algorithms. We propose a simple volume-correction approach that incorporates an analytical approximation of the truncated volume to correct for the missing droplet/bubble volumes. This proposed method results in accurately recovering the dispersed phase volumes with minimal volume error over a wide range of volume fraction cutoff values;and hence, can also accurately recover the number of droplets/bubbles. This can be a valuable tool for accurate calculation of drop/bubble size distributions for analysis and for Eulerian-to-Lagrangian conversion of the dispersed phase in multi-scale modeling approaches. © 2025, CC BY.

关键词： Two phase flow

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Transition Measurements on the SWiFT Model in the National Transonic Facility

Transition Measurements on the SWiFT Model in the National T...

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AIAA Science and technology Forum and Exposition, AIAA SciTech Forum 2025

作者： Eppink, Jenna L. Sadowski, Shelly Andino, Marlyn Chan, David Moran, Bryce Flow Physics and Control Branch NASA Langley Research Center MS 170 HamptonVA23681 United States Configuration Aerodynamics Branch NASA Langley Research Center MS 499 HamptonVA23681 United States Jacobs Technology Inc NASA Langley Research Center Mail Stop 267 HamptonVA23681 United States

ISBN: (数字)9781624107238

ISBN: (纸本)9781624107238

Boundary layer transition locations on the Swept Wing flow Test (SWiFT) Hybrid Wing Body model were measured in the National Transonic Facility (NTF) at the NASA Langley Research Center using several different methods. These methods include sublimating chemical f low visualization for a limited number of low Reynolds number conditions, as well as mean static pressure and dynamic pressure measurements. Results are presented for a range of conditions in the NTF, demonstrating Mach and Reynolds number effects. The transition front locations obtained from the different techniques agree well. A variation of the static pressure transition detection method is described in which continuous angle of attack polars are performed. This approach enables detection of the transition front at more challenging (high Reynolds number) conditions than is possible with sparser data from pitch-pause angle-of-attack polars. The trip dot effectiveness is also verified using all of the available diagnostics. Additionally, low Reynolds number results are compared with those acquired on the same model at the Aircraft Research Association (ARA) facility, and these results show good agreement overall, suggesting similar freestream flow quality conditions of the two facilities. © 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： NASA

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Laser structuring of thin metal films 23

Laser structuring of thin metal films

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23rd International Conference and School on Quantum Electronics, ICSQE 2024

作者： Nedyalkov, N.N. Atanasov, P.A. Dikovska, A.O. Grochowska, K. Karczewski, J. Sawczak, M. Jendrzejewski, R. Institute of Electronics Bulgarian Academy of Sciences 72 Tsarigradsko Chaussee Sofia1784 Bulgaria The Szewalski Institute of Fluid-Flow Machinery Polish Academy of Sciences 14 Fiszera Str. Gdansk80-231 Poland Faculty of Applied Physics and Mathematics Institute of Nanotechnology and Materials Engineering University of Technology Narutowicza 11/12 Street Gdansk80-233 Poland

This work presents results on structuring of thin gold/silver (AuAg) composite film by laser pulses with different pulse durations. Laser systems that generate millisecond (50 ms), nanosecond (15 ns), picosecond (10 ps), and femtosecond (100 fs) pulses are used in the experiments. The laser wavelength is 1064 nm for ms, ns, and ps regime and 800 nm for the femtosecond one. The metal films are deposited by pulsed laser deposition technique on quartz substrates using nanosecond laser pulses. The surface morphologies induced by variation of the processing parameters as pulse duration and applied laser fluence are studied. It is found that the laser processing results in formation of variety of micro- and nanostructures, with characteristics that can be controlled by the laser parameters. The obtained structures express optical properties defined by the plasmon excitation. The fabricated structures show efficiency as active substrates in Surface Enhanced Raman Spectroscopy. © 2025 Institute of physics Publishing. All rights reserved.

关键词： Pulsed laser deposition

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Magnetic properties of monolayer VS2 with or without point defects

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Physica E: Low-Dimensional Systems and Nanostructures 2025年 172卷

作者： Lu, Jingsong Huang, Can Liu, Bingjie Pan, Yanfei Fan, Jiyu Ma, Chunlan Zhu, Yan MIIT Nanjing University of Aeronautics and Astronautics Nanjing210016 China Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application School of Mathematics and Physics Suzhou University of Science and Technology Suzhou215009 China Advanced Technology Research Institute of Taihu Photon Center School of Physical Science and Technology Suzhou University of Science and Technology Suzhou215009 China

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are becoming increasingly attractive and beneficial to the development of spintronic devices and integrated circuit technologies. The magnetism of monolayer vanadium disulfide remains debated, with no consensus on whether it exhibits ferromagnetism or remains non-magnetic at room temperature. Herein, based on first-principles calculations, we study the stability and electronic structure of monolayer VS2 in the 1T and 2H phases. Both phases are ferromagnetic ordering in the ideal structure and the magnetic exchange parameters are obtained through the spin-spiral method. Moreover, through the Monte Carlo simulator, we simulate the variation of magnetic parameters along with the increase in temperature. Finally, according to the Stoner criterion, the magnetic moment around the V point defect may collapse due to the decrease in the density of states at the Fermi level. This provides a theoretical explanation for the prevalent absence of observation of net magnetic moments in experiments. © 2025 Elsevier B.V.

关键词： Point defects

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Stationary states of forced two-phase turbulence

arXiv

引用

arXiv 2025年

作者： Jain, Suhas S. Elnahhas, Ahmed Flow Physics and Computational Science Lab George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology GA United States Center for Turbulence Research Stanford University CA United States

In this work, we perform numerical simulations of forced two-phase isotropic turbulence to study the stationary states of a two-phase mixture. We first formulate three different approaches to force a two-phase turbulent flow that maintains a constant (a) mixture kinetic energy, (b) mixture kinetic energy + surface energy, and (c) individual phase kinetic energy, and study their effect on the final stationary state of the system. We show that forcing the two-phase system eliminates the arbitrariness associated with the initialization of the second phase in two-phase turbulence simulations. Next, we study the global statistics of the two-phase mixture in the stationary state for varying density ratios (10−3 to 103) and viscosity ratios (10−3 to 103), void fraction (dilute to dense regimes), and Weber numbers (breakup and non-breakup regimes). We utilize a spatial filtering approach, that is applicable for the general case of incompressible/compressible two-phase flows, to compute the energy spectra of each of the phases and study the turbulent kinetic energy distribution across scales. We find that the interface behaves as a soft wall, inhibiting the accommodation of eddies inside the dispersed phase. Finally, we show that bubbles and drops exhibit different turbulent characteristics for the same global conditions of the carrier phase, with bubbles exhibiting higher turbulent intensities inside them and droplets behaving ballistically, similar to solid particles. This study acts as a foundational work on stationary two-phase turbulence, which can be used for further analysis and the development of subgrid-scale models for larger-scale simulations of two-phase turbulent flows. © 2025, CC BY.

关键词： Wakes

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