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Comparison of the high-order Runge-Kutta discontinuous Galerkin method and gas-kinetic scheme for inviscid compressible flow simulations

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arXiv

arXiv 2024年

关键词： Runge Kutta methods

A Compact Gas-Kinetic Scheme with Scalable Geometric Multigrid Acceleration for Steady-State Computation on 3D Unstructured Meshes

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arXiv

arXiv 2024年

作者： Liu, Hongyu Ji, Xing Mao, Yunpeng Ding, Yuan Xu, Kun Shaanxi Key Laboratory of Environment and Control for Flight Vehicle Xi'an Jiaotong University Xi’an China Department of Mathematics Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong Department of Mechanical and Aerospace Engineering Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong Shenzhen Research Institute Hong Kong University of Science and Technology Shenzhen China

In this paper, we present an advanced high-order compact gas-kinetic scheme (CGKS) for 3D unstructured mixed-element meshes, augmented with a geometric multigrid technique to accelerate steady-state convergence. The scheme evolves cell-averaged flow variables and their gradients on the original mesh. Mesh coarsening employs a two-step parallel agglomeration algorithm using a random hash for cell interface selection and a geometric skewness metric for deletion confirmation, ensuring both efficiency and robustness. For the coarser meshes, first-order kinetic flux vector splitting (KFVS) schemes with explicit or implicit time-stepping are used. The proposed multigrid CGKS is tested across various flow regimes on hybrid unstructured meshes, demonstrating significant improvements. A three-layer V-cycle multigrid strategy, coupled with an explicit forward Euler method on coarser levels, results in a convergence rate up to ten times faster than standard CGKS. In contrast, the implicit lower-upper symmetric Gauss-Seidel (LU-SGS) method offers limited convergence acceleration. Our findings indicate that the explicit multigrid CGKS is highly scalable and effective for large-scale computations, marking a substantial step forward in computational fluid dynamics. Copyright © 2024, The Authors. All rights reserved.

关键词： Computational fluid dynamics

A Memory Reduction Compact Gas Kinetic Scheme on 3D Unstructured Meshes

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arXiv

arXiv 2024年

作者： Liu, Hongyu Ji, Xing Mao, Yunpeng Qian, Zhe Xu, Kun Shaanxi Key Laboratory of Environment and Control for Flight Vehicle Xi’an Jiaotong University Xi’an China Department of Mathematics Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong Department of Mechanical and Aerospace Engineering Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong Shenzhen Research Institute Hong Kong University of Science and Technology Shenzhen China

This paper presents a memory-reduction third-order compact gas-kinetic scheme (CGKS) designed to solve compressible Euler and Navier-Stokes equations on 3D unstructured meshes. Utilizing the time-accurate gas distribution function, the gas kinetic solver provides a time-evolution solution at the cell interface, distinguishable from the Riemann solver with a constant solution. With the time evolution solution at the cell interface, evolving both the cell-averaged flow variables and the cell-averaged slopes of flow variables becomes feasible. Therefore, with the cell-averaged flow variables and their slopes inside each cell, the Hermite WENO (HWENO) techniques can be naturally implemented for the compact high-order reconstruction at the beginning of the next time step. However, the HWENO reconstruction method requires the storage of a reconstruction-coefficients matrix for the quadratic polynomial to achieve third-order accuracy, leading to substantial memory consumption. This memory overhead limits both computational efficiency and the scale of simulations. A novel reconstruction method, built upon HWENO reconstruction, has been designed to enhance computational efficiency and reduce memory usage compared to the original CGKS. The simple idea is that the first-order and second-order terms of the quadratic polynomials are determined in a two-step way. In the first step, the second-order terms are obtained from the reconstruction of a linear polynomial of the first-order derivatives by only using the cell-averaged slopes, since the second-order derivatives are nothing but the"derivatives of derivatives". Subsequently, the first-order terms left can be determined by the linear reconstruction only using cell-averaged values. Thus, we successfully split one quadratic least-square regression into several linear least-square regressions, which are commonly used in a second-order finite volume code. Since only a 3 × 3 matrix inversion is needed in a 3-D linear least-square r

关键词： Navier Stokes equations

Detailed Investigation for Inhibitory Mechanism in Iron-Based Composites with Bifunction of Anti-Corrosion and Electromagnetic Wave Absorption Founded on Experiments and Theoretical Computations

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SSRN 2024年

作者： Jiang, Xianyu Xie, Jianlian Yin, Liangjun Peng, Jian Li, Jianxiao Jiang, Xian Yu Zhang, Min Qin, Huanyu Jing, Zhi Yuan, Le Zhang, Linbo Deng, Longjiang Zhang, Peng National Engineering Research Center of Electromagnetic Radiation Control Materials Key Laboratory of Multi-spectral Absorbing Materials and Structures Ministry of Education University of Electronic Science and Technology of China 2006 Xiyuan Road Chengdu611731 China Shenyang Aircraft Design and Research Institute Aviation Industry Corporation of China Ltd Shenyang110034 China Key Laboratory of Materials and Surface Technology Ministry of Education School of Materials Science and Engineering Xihua University Sichuan Chengdu610039 China

In this study, 2-benzothiazolylthio-succinic acid (BTSA) and trimethoxy (octadecyl) silane (OTMS) are synthesized as anti-corrosion coating to inhibit the corrosion of carbonyl iron (CI) in salt-containing environment. Electrochemical experimental affirmed that the CI@BTSA@OTMS composites exhibited exceptional anti-corrosion with the corrosion current (Icorr) was as low as 1.1 × 10−7 A/cm−2, and the protection efficiency reached 99.91%. After 720 hours of exposure in a natural salt spray test, the composites still retained relatively intact morphological and compositional characteristics. Molecular dynamics simulations and quantum chemical calculations are used to reveal the diffusion and inhibition mechanisms of corrosive species. © 2024, The Authors. All rights reserved.

关键词： Corrosion resistance

Layered Fe-Doped Srlaino 4 Perovskite Electron Transport Layer for Dye-Sensitized Solar Cell with High Open-Circuit Voltage

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SSRN 2023年

作者： Xie, Yuan Gu, Mengmeng Chen, Minghan Cao, Li Zhang, Shaoqing Wang, Yanping Niu, Feier Yan, Haoran Civil Aircraft Fire Science and Safety Engineering Key Laboratory of Sichuan Province Civil Aviation Flight University of China Guanghan618307 China College of Chemistry and Materials Engineering Anhui Science and Technology University Bengbu233030 China Anhui Quartz Sand Purification and Photovoltaic Glass Engineering Research Center Anhui Science and Technology University Bengbu233030 China

This study presents the synthesis of SrLaInO4 perovskite oxides using a high-temperature solid-phase method under atmospheric pressure, with varying Fe-doping concentrations incorporated during fabrication. The synthesized particles underwent characterization using X-ray diffraction and electron microscopy, revealing a layered crystal structure. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy were employed to confirm the successful incorporation of Fe into the SrLaInO4 crystal structure. Significantly, Fe-doping was observed to broaden the light absorption range of the perovskite oxide whilst simultaneously reducing the bandgap. When employed as the electron transport layer in dye-sensitized solar cells, Fe-doped SrLaInO4 perovskite exhibited a maximum efficiency of 4.64%, alongside an open-circuit voltage (VOC) of 0.801 V, which was noticeably higher than that observed in identically-prepared cells employing TiO2 as the electron transport layer. © 2023, The Authors. All rights reserved.

关键词： Open circuit voltage

Learning Adaptive Feature for Object Detection in Low-Light Conditions

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SSRN 2023年

作者： Fu, Gui Chu, Hongyu Tu, Xiaoguang Huang, Yi Liu, Liwen He, Zhi Zhang, Chao Zhang, Chengfang Zhang, Xiaoqiang School of Information Engineering Southwest University of Science and Technology Mianyang621010 China Institute of Electronic and Electrical Engineering Civil Aviation Flight University of China Guanghan618307 China Intelligent Policing Key Laboratory of Sichuan Province Sichuan Police College Luzhou646099 China

In low-light conditions, object detection algorithms suffer from reduced accuracy due to factors like noise and insufficient information. Current solutions often involve a two-stage process: first, improving image illumination, and then performing object detection. However, this method has limitations, as these networks work independently. To address this, we propose a parallel object detection algorithm for low-light environments. Our approach simultaneously encodes image features using both an illumination enhancement network and an object detection network. This innovative design allows these networks to adapt to each other, improving feature adaptability for object detection. We enhance adaptive learning efficiency by introducing a novel mutual feedback mechanism, dynamically adjusts the learning weights of the two networks, thereby enhancing the network's capacity to encode object-related information in low-light conditions. We conducted experiments on both the real-world and synthetic datasets, the results demonstrate that the proposed method outperforms the other state-of-the-art approaches in low-light environments. © 2023, The Authors. All rights reserved.

关键词： Object detection

A Constructive Semi-global Differential Game Design Method for Multi-agent Systems under Input Constraint and Collision Avoidance

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A Constructive Semi-global Differential Game Design Method f...

2021 China Automation Congress, CAC 2021

作者： Wu, Xiongjun Zhou, Jialing Li, Yuanlong Chen, Chunfang Li, Kai The 802 Institute of Shanghai Academy of Space Flight Technology Eighth Academy of China Aerospace Science and Technology Corporation National Defense Key Laboratory of Science and Technology on Electromagnetic Scattering Shanghai201109 China School of Automation Nanjing University Science and Technology Nanjing210094 China Department of Automation Shanghai Jiao Tong University Key Laboratory of System Control and Information Processing Ministry of Education of China Shanghai200240 China The 802 Institute of Shanghai Academy of Space Flight Shanghai210094 China School of Automation Science and Electrical Engineering Beihang University Beijing100191 China

ISBN: (纸本)9781665426473

The constructive semi-global differential game concept is introduced into the multi-agent's cooperative controller designing of typical autonomous unmanned systems subject to controller input constraint as well as the collision avoidance requirements simultaneously. The problem of driving each agent which is assume to subject to input constraint nonlinearity from the initial position to a desired one and at the same time avoiding collisions (referring to both static obstacles and other agents) is modeled and transformed into multi-agent's collision avoidance problem. In view of the requirement that different agents working together might possibly have individual but conflicting purpose (such as in the multi-missile cooperative detection requiring slowly and continuing actions vs fast formation control scenario, and multi-agents' fast arriving vs avoiding different kinds of obstacles). The differential game theory provided a mechanism or framework for investigating different kinds of problems in which several players seek to achieve individual purposes or goals, which might be competing rather than cooperation. In view of the input constraints, the problem is reduced as a semi-global differential game. Conditions are established to guarantee input constraints are satisfied, and mainly by using the Hamilton-Jacobi-Isaacs (HJI for short) PDIs and as well as Ε-Nash equilibria. The semi-global property of the states are also guaranteed. It provides a description in terms of the invariant set for the overall differential game system under constraint controller input. Illustrative examples are carried out to verify the effectiveness of the method, and also the feasibility of the suggested control protocols. © 2021 IEEE

关键词： Multi agent systems

A vision-based navigation method for eVTOL final approach in urban air mobility(UAM) 4

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A vision-based navigation method for eVTOL final approach in...

4th CAA International Conference on Vehicular control and Intelligence, CVCI 2020

作者： Ye, Siyuan Wan, Zeyu Zeng, Long Li, Chenglong Zhang, Yu College of Aeronautical Engineering Civil Aviation Flight University of China Guanghan618307 China College of Control Science and Engineering Zhejiang University Hangzhou310027 China College of Air Traffic Management Civil Aviation Flight University of China Guanghan618307 China Civil Aviation Flight University of China Department of Navigation Engineering Guanghan618307 China State Key Laboratory of Industrial Control Technology College of Control Science and Engineering Zhejiang University Hangzhou310027 China

ISBN: (纸本)9781728184968

Urban air mobility(UAM) is an emerging way of air transportation by using self-pilot electric vertical takeoff and landing (eVTOL) vehicles to transport people and cargo in an urban area. The final approach is the critical stage in the operation. Accurate location information and vertical height guidance are needed in this stage. In addition to the common GNSS/INS integrated navigation system, this work proposes an independent vision-based method to provide redundant location information in the final approach for eVTOL vehicles. The simulation results show that the positioning accuracy of the visual method is within 1.5 meters when the vehicles are no more than 25 meters away from the reference place. © 2020 IEEE.

关键词： Air mobility

Energy Efficient Path Planning for Autonomous Ground Vehicles With Ackermann Steering

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SSRN 2022年

作者： Zhang, Haojie Zhang, Yudong Liu, Chuankai Zhang, Zuoyu School of Automation and Electrical Engineering University of Science and Technology Beijing Beijing100083 China Beijing Aerospace Control Center Beijing100094 China Key Laboratory of Science and Technology on Space Flight Dynamics Beijing100094 China

As the demand for autonomous ground vehicle to perform tasks in outdoor environment is increasing, it becomes more important to reduce energy cost in order to perform more tasks more efficiently with limit energy supply. Recent research has developed an effective methodology for generating dynamically feasible, energy efficient trajectories for skid steering or differential steering autonomous ground vehicles. Taking into account the demand for reducing energy cost and improving the quality of generated path, an energy efficient path planning method with guarantee on completeness is proposed for autonomous ground vehicle with ackermann steering which is based on A* search algorithm. Firstly, the energy cost model is established for the autonomous ground vehicle using its kinematic constraints. Then, given the start and goal states, the energy-aware motion primitives are generated offline using the energy cost model to calculate the cost of each primary trajectory. Lastly, the energy efficient path planner is proposed and the analysis for completeness properties is given. The effectiveness of the proposed energy efficient path planner is verified by lots of simulation and real vehicle tests. The results show that a small increase in the distance of a path over the distance optimal path can result in a dramatic savings in the energy cost for autonomous ground vehicles with ackermann steering. © 2022, The Authors. All rights reserved.

关键词： Automobile steering equipment