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4th International Conference on Defence Technology, ICDT 2024

作者： Zhao, Juncheng Gong, Zheng Yang, Yi Chen, Yongliang Bai, Yalei Department of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing210016 China National Key Laboratory of Helicopter Dynamics Nanjing University of Aeronautics and Astronautics Nanjing210016 China Key Lab. of Unsteady Aerodynamics and Flow Contr. of Ministry of Industry and Information Technology Nanjing University of Aeronautics and Astronautics Nanjing210016 China

On the modern battlefield, suicide drones have a low ability to break through the air defense fire network when using traditional ballistics against ground targets. The adoption of ballistic trajectory with landing constraints can effectively improve the survivability of missiles and the attacking effect on ground targets. Starting from the pure proportional navigation, the relationship between the ballistic angular rate and the target line-of-sight angular rate of the traditional proportional guidance is expanded to the relationship between the missile's overload and the target's line-of-sight angle, so as to realize the effect of controlling the missile's overload to indirectly control the ballistic angle to the target's line-of-sight angle of convergence, which ensures the fast tracking of the target and at the same time, makes the missile attack the target's trajectory more gently. Attacking the target with the overload control method guarantees that the overload of the missile during the guidance process is within a reasonable range, which effectively reduces the probability of missing the target. By selecting appropriate proportional navigation coefficients and incorporating bias terms with controlled descent angles, a three-dimensional guidance and control method is designed to achieve precise targeting with longitudinal descent angle constraints on fixed ground targets. This guidance and control method remains effective even under hypersonic conditions, as verified through hardware-in-theloop simulation, confirming its effectiveness and precision. © 2024 Institute of Physics Publishing. All rights reserved.

关键词： Ballistics

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High-order flux reconstruction thermal lattice Boltzmann flux solver for simulation of incompressible thermal flows

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Physical Review E 2022年第3期106卷 035301-035301页

作者： Chao Ma Jie Wu Xiangyu Gu Liming Yang State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Yudao Street 29 Nanjing Jiangsu 210016 China Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information Technology and Department of Aerodynamics Nanjing University of Aeronautics and Astronautics Yudao Street 29 Nanjing Jiangsu 210016 China China Academy of Launch Vehicle Technology Nandahongmen Street 1 Beijing 100076 China

In this paper, a high-order solver combining the flux reconstruction (FR) method and the thermal lattice Boltzmann flux solver (FRTLBFS) is developed for accurately and efficiently simulating incompressible thermal flows. The conservative differential equations recovered from Chapman-Enskog analysis of the thermal lattice Boltzmann equation are solved by the high-order FR method. The thermal lattice Boltzmann method is only applied to reconstruct the local solution used for evaluating fluxes at the solution and flux points. Unlike the traditional Navier-Stokes–Boussinesq (NSB) solvers where the inviscid and viscous terms are treated separately, the inviscid and viscous fluxes in the current FRTLBFS are coupled and computed uniformly. In comparison with the recently developed high-order flux reconstruction thermal lattice Boltzmann method, the FRTLBFS holds advantages such as high-order accuracy, good stability, and compactness but is more efficient and low storage, since only macroscopic flow variables including density, velocity, and temperature are stored and evolved. In addition, the physical boundary conditions in FRTLBFS can be directly implemented by using the same method as in conventional NSB solvers. Numerical validations of the proposed method are implemented by simulating (a) the porous plate problem, (b) natural convection in a square cavity, (c) unsteady natural convection in a tall cavity, and (d) thermal lid-driven cavity flow. Numerical results demonstrate that the present solver is an attractive tool to simulate incompressible thermal flows due to its high-order accuracy, stability, and low memory cost.

关键词： Convection Porous media Lattice-Boltzmann methods

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Discrete unified gas-kinetic wave-particle method for flows in all flow regimes

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Physical Review E 2023年第1期108卷 015302-015302页

作者： L. M. Yang Z. H. Li C. Shu Y. Y. Liu W. Liu J. Wu State Key Laboratory of Mechanics and Control for Aerospace Structures Nanjing University of Aeronautics and Astronautics Nanjing 210016 China MIIT Key Laboratory of Unsteady Aerodynamics and Flow Control Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Department of Aerodynamics College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center Mianyang 621000 China National Laboratory for Computational Fluid Dynamics Beihang University Beijing 100191 China Department of Mechanical Engineering National University of Singapore Singapore 117576 Singapore

This work proposes a discrete unified gas-kinetic wave-particle (DUGKWP) method for simulation of flows in all flow regimes. Unlike the discrete velocity method (DVM) and the direct simulation Monte Carlo (DSMC) method which solve the governing equations by either the deterministic method or the stochastic method, the DUGKWP combines the advantages of these two methods. In the DUGKWP, the information of microscopic particles as well as macroscopic flow variables are both evolved. Specifically, the microscopic particles are updated by the free-transport and resampling processes, while the macroscopic flow properties are evolved via solving the macroscopic governing equations of conservation laws with the finite volume method. According to the discrete characteristic solution to the Boltzmann-BGK equation utilized in the DUGKWP, in the highly rarefied flow regime, the motion of microscopic particles greatly determines the fluxes for the macroscopic governing equations. Conversely, for the continuum flow, no microscopic particle exists in the computational domain and the DUGKWP is degraded to the Navier-Stokes solver. Numerical studies validate that the DUGKWP can accurately predict the flow properties in all flow regimes. Furthermore, compared with the deterministic method, the DUGKWP enjoys superior efficiency with less memory consumption for both high-speed rarefied flows and flows close to the continuum regime.

关键词： Compressible flows Kinetic theory Rarefied flows

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Improvement of the Accuracy and the Efficiency of the Sph: Point Generation and Adaptive Particle Refinement/Coarsening Algorithms

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SSRN 2023年

作者： Zhang, Jun Wu, Wei Li, Wenjie Zhang, Zhaoming Jiao, Yanmei Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information Technology Nanjing University of Aeronautics and Astronautics Nanjing210000 China School of Physical and Mathematical Sciences Nanjing Tech University Nanjing211816 China

An adaptive particle refinement (APR) algorithm has been developed for the smooth particle hydrodynamics (SPH) method to increase the resolution of the region of interest to achieve high accuracy and simultaneously reduce the cost in computational resources. However, the existing APR algorithms widely suffer from computational dispersion at the interface of regions of different particle resolutions. In addition, traditional shifting algorithm applied in the APR processes also have difficulties in dealing with particles with different smooth lengths. In this work, an algorithm for fast particle generation is first developed based on the accelerated ray method, which accelerates the discretization of the flow field into particles. Then a dynamic refinement/coarsening algorithm based on the APR algorithm is proposed to solve the computational dispersion problem occurring at the refinement/coarsening interfaces. In addition, the shifting algorithm is improved in this work to make the particles always well distributed during numerical calculations and thus efficiently facilitate the adaptive particle refinement/coarsening processes. Comparison results show that the robust algorithms developed for the SPH method in this work can lead to more precise and reasonable flow fields compared with the conventional SPH adaptive methods. © 2023, The Authors. All rights reserved.

关键词： Image segmentation

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Improvement of the Accuracy and the Efficiency of the Sph: Point Generation and Adaptive Particle Refinement/Coarsening Algorithms

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SSRN 2023年

关键词： Image segmentation

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Phase difference effect on collective locomotion of two tandem autopropelled flapping foils

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Physical Review Fluids 2019年第5期4卷 054101-054101页

作者： Xingjian Lin Jie Wu Tongwei Zhang Liming Yang Department of Aerodynamics Nanjing University of Aeronautics and Astronautics Yudao Street 29 Nanjing Jiangsu 210016 China Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information Technology Nanjing University of Aeronautics and Astronautics Yudao Street 29 Nanjing Jiangsu 210016 China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Yudao Street 29 Nanjing Jiangsu 210016 China Department of Mechanical Engineering National University of Singapore 10 Kent Ridge Crescent Singapore 119260

The effect of phase difference on the collective locomotion of two tandem flapping foils is numerically studied in this paper. The numerical results indicate that the collective locomotion is greatly affected by the phase difference. Two distinct collective modes are observed, i.e., the fast mode and the slow mode. The fast mode is only observed in part of the range of the phase difference (ϕ), i.e., ϕ=0.0−0.1π and 1.5π–1.9π with appropriate initial distance, and the slow mode appears in the range of ϕ=0.3π−1.4π. Meanwhile, the follower of the two foils has hydrodynamic benefit in both fast and slow modes, and it can obtain the highest efficiency in the fast mode at ϕ=1.6π. However, the leader can only achieve hydrodynamic benefit in the fast mode, and the highest efficiency occurs at ϕ=0.1π. In addition, the stable distance between two foils in the slow mode can be quantized with the phase difference. Furthermore, the fluid-structure interactions between two foils are also analyzed. Two distinct vortex interactions are observed in the fast mode, i.e., merging interaction and broken interaction, which, respectively, result in the highest propulsive efficiency for the follower and the leader. In the merging interaction, the leading edge vortex of the leader is captured by the follower, which results in the weak trailing edge vortex of the leader but a strong trailing edge vortex of the follower. In the broken interaction, the leading edge vortex of the follower sheds into the wake together with the trailing edge vortex of the leader, and induces the trailing edge vortex of the follower to be broken into two parts. Which kind of vortex interaction occurs depends on the phase difference. The results obtained here may provide some light on understanding the coordinated behavior of biological collectives.

关键词： Locomotion Immersed boundary methods Navier-Stokes equation

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Discrete Unified Gas-Kinetic Wave-Particle Method for flows in All flow Regimes

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SSRN 2022年

作者： Yang, L.M. Li, Z.H. Shu, C. Liu, Y.Y. Liu, W. Wu, J. Department of Aerodynamics College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing210016 China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Nanjing210016 China Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information Technology Nanjing210016 China Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center Mianyang621000 China National Laboratory for Computational Fluid Dynamics Beijing100191 China Department of Mechanical Engineering National University of Singapore Singapore117576 Singapore

This work proposes a discrete unified gas-kinetic wave-particle (DUGKWP) method for simulation of flows in all flow regimes. Unlike the discrete velocity method (DVM) and the direct simulation Monte Carlo (DSMC) method which solve the governing equations by either the deterministic method or the stochastic method, the DUGKWP combines the advantages of these two methods. In the DUGKWP, the information of microscopic particles as well as macroscopic flow variables are both evolved. Specifically, the microscopic particles are updated by the free-transport and resampling processes, while the macroscopic flow properties are evolved through solving the macroscopic governing equations of conservation laws with the finite volume method. According to the discrete characteristic solution to the Boltzmann-BGK equation utilized in the DUGKWP, in the highly rarefied flow regime, the motion of microscopic particles greatly determines the fluxes for the macroscopic governing equations. Conversely, for the continuum flow, no microscopic particle exists in the computational domain and the DUGKWP is degraded to the Navier-Stokes’ solver. Numerical studies validate that the DUGKWP can accurately predict the flow properties in all flow regimes. Furthermore, compared with the deterministic method, the DUGKWP enjoys superior efficiency with less memory consumption for both high-speed rarefied flows and flows close to the continuum regime. © 2022, The Authors. All rights reserved.

关键词： Navier Stokes equations

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A GPU-Accelerated Discontinuous Galerkin Method for Solving Two-Dimensional Laminar flows

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Transactions of Nanjing University of Aeronautics and Astronautics 2022年第4期39卷 450-466页

作者： GAO Huanqin CHEN Hongquan ZHANG Jiale XU Shengguan GAO Yukun Key Laboratory of Non-steady Aerodynamics and Flow Control of MIIT College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China School of Mechanical Engineering Anhui University of TechnologyMaanshan 243002P.R.China

A graphics processing unit(GPU)-accelerated discontinuous Galerkin(DG)method is presented for solving two-dimensional laminar *** DG method is ported from central processing unit to GPU in a way of achieving GPU speedup through programming under the compute unified device architecture(CUDA)*** CUDA kernel subroutines are designed to meet with the requirement of high order computing of DG *** corresponding data structures are constructed in component-wised manners and the thread hierarchy is manipulated in cell-wised or edge-wised manners associated with related integrals involved in solving laminar Navier-Stokes equations,in which the inviscid and viscous flux terms are computed by the local lax-Friedrichs scheme and the second scheme of Bassi&Rebay,respectively.A strong stability preserving Runge-Kutta scheme is then used for time marching of numerical *** resulting GPU-accelerated DG method is first validated by the traditional Couette flow problems with different mesh sizes associated with different orders of approximation,which shows that the orders of convergence,as expected,can be *** numerical simulations of the typical flows over a circular cylinder or a NACA 0012 airfoil are then carried out,and the results are further compared with the analytical solutions or available experimental and numerical values reported in the literature,as well as with a performance analysis of the developed code in terms of GPU *** shows that the costs of computing time of the presented test cases are significantly reduced without losing accuracy,while impressive speedups up to 69.7 times are achieved by the present method in comparison to its CPU counterpart.

关键词： discontinuous Galerkin GPU compute unified device architecture(CUDA) Navier-Stokes equation laminar flows

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Information Preservation Optimization Method Based on the Advection Upstream Splitting Method in Supersonic Rarefied flow Simulation

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SSRN 2022年

作者： Xu, Xiao Ma, Xinjian Zhang, Jun Shen, Yan Zhang, Junyan School of Mechatronics and Power Engineering Jiangsu University of Science and Technology Zhangjiagang215600 China Shanghai Space Propulsion Technology Research Institute Shanghai201109 China Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information Technology Nanjing University of Aeronautics and Astronautics Nanjing210016 China China Academy of Aerospace Aerodynamics Beijing100074 China

An information preservation (IP) optimization approach for supersonic flow simulation is proposed in this paper. According to the conversion of the variables integrated in half-space and the analogical analysis, a similarity relationship between the integrated variables in the governing equations of the preserved information and macroscopic variables in Navier-Stokes equations is obtained. The computational approach of the flux for the correlation terms is reconstructed using the Advection Upstream Splitting Method (AUSM) scheme, giving the IP method windward characteristics. Additionally, the pressure boundary treatment is modified to improve the stability and accuracy of the IP method in the simulation of rarefied supersonic flow driven by high pressure. The particle number threshold method is proposed to solve the "carbuncle point" problem caused by insufficient local collisions. The IP optimization method combines the advantages of the AUSM scheme and the low statistical scatter method;thus, it can accurately and effectively investigate real-time variation characteristics of rarefied supersonic flow. This method simulates the supersonic microscale jet flow and hypersonic macroscale nozzle flow. The results indicate that the real-time statistical accuracy of the IP optimization method is much better than the direct simulation Monte Carlo method, whereas the correctness and accuracy of this method are satisfactory. Therefore, the proposed method provides an efficient algorithm for the variation mechanism and unsteady flow-characteristic research on rarefied supersonic flow on different scales. © 2022, The Authors. All rights reserved.

关键词： Supersonic flow

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Aerodynamic Prediction and Design Optimization Using Multi-Fidelity Deep Neural Network

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SSRN 2024年

作者： Du, Bingchen Guo, Tongqing Wu, Jiangpeng Zhou, Di Lu, Zhiliang Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information Technology Nanjing University of Aeronautics and Astronautics 29 Yudao St. Qinhuai District Jiangsu Nanjing210006 China AVIC Shenyang Aircraft Design and Research Institute 40 Tawan St. Huanggu District Liaoning Shenyang110035 China

With the rapid development of data-driven methods in recent years, deep neural networks have attracted significant attention for aerodynamic predictions and design optimizations. Among these methods, the multi-fidelity deep neural network (MFDNN), which can combine high- fidelity (HF) and low-fidelity (LF) data, has gained popularity. This paper systematically investigates the performances of employing MFDNN models in predicting aerodynamic coefficients and in performing aerodynamic shape optimizations (ASOs), especially the impact of using various HF/LF data ratios for training models. The results of the prediction accuracy show that the less HF data used, the more advantages can be achieved by the MFDNN models than the single-fidelity models. The well-trained MFDNN models are then employed in an ASO problem, and it is found that a higher HF/LF data ratio does not definitely result in a better performance in the ASO. As the insufficiency in the prediction accuracy of the optimal shapes appears when employing the non-updated MFDNN models, an update strategy is developed by tightly integrating the MFDNN models with the particle swarm optimization algorithm. To further reduce the time costs for updating models, a dual-threshold update strategy is then introduced, which can half the counts of evaluating HF data. © 2024, The Authors. All rights reserved.

关键词： Shape optimization

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