检索结果-内蒙古大学图书馆

A Viscous-Term Subcell Limiting Approach for High-Order Fr/Cpr Method in Solving Compressible Navier-Stokes Equations on Curvilinear Grids

学校读者我要写书评

暂无评论

SSRN 2023年

作者： Zhu, Huajun Yan, Zhen-Guo Liu, Huayong Mao, Meiliang Deng, Xiaogang State Key Laboratory of Aerodynamics China Aerodynamics Research and Development Center Sichuan Mianyang621000 China Tianfu Engineering-Oriented Numerical Simulation & Software Innovation Center Sichuan University Sichuan Chengdu610000 China Chinese Academy of Military Science Beijing100071 China

High-order flux reconstruction/correction procedure via reconstruction (FR/CPR) method has become an attractive method for simulating multi-scale flows because of their high accuracy and low dissipation. However, simulating flows with strong shocks is still challenging for FR/CPR. Recently, a priori subcell limiting based on compact nonlinear nonuniform weighted (CNNW) schemes was proposed for the CPR method to solve the Euler equations, which robustly simulates strong shocks and has good balance between high resolution and shock capturing robustness. The CPR method with subcell CNNW limiting is a hybrid scheme and also called hybrid CPR-CNNW scheme (abbr. HCCS). This paper extends HCCS to solve compressible Navier-Stokes equations on curvilinear grids. To improve the capability of HCCS in simulating hypersonic flows, a viscous-term subcell limiting (VSL) approach is proposed. The main idea of the VSL is to replace the unified high-order polynomial distribution by limited piecewise polynomial distribution in troubled cells for the viscous-term discretization, which is implemented by decomposing the troubled cells into subcells and limiting the distribution of physical variables for each subcells. In this paper, the VSL reuses the limited results of subcell CNNW schemes used in the inviscid-term discretization, which makes the approach efficient. It is shown that HCCS without the VSL blows up during simulating hypersonic flows. Then, HCCS with the VSL is extended to curvilinear grids. Discrete grid metrics and discrete Jacobian are designed to make HCCS with the VSL satisfy discrete conservation laws, discrete geometric conservation laws and fulfilling free-stream preservation, which are validated by two test cases on curvilinear grids. numerical results on several typical cases show that HCCS with the VSL has superiority in high resolution, shock capturing robustness, and accurate prediction of surface pressure, skin friction and heat transfer. © 2023, The Authors.

关键词： Navier Stokes equations

Unsupervised Learning Method for the Wave Equation Based on Finite Difference Residual Constraints Loss

学校读者我要写书评

暂无评论

arXiv

arXiv 2024年

作者： Feng, Xin Jiang, Yi Qin, Jia-Xian Zhang, Lai-Ping Deng, Xiao-Gang College of Computer Science Sichuan University Chengdu610065 China Tianfu Engineering-oriented Numerical Simulation & Software Innovation Center Sichuan University Chengdu610000 China PLA Beijing100082 China Institute of Defense Science and Technology Innovation Academy of Military Sciences Beijing100071 China

The wave equation is an important physical partial differential equation, and in recent years, deep learning has shown promise in accelerating or replacing traditional numerical methods for solving it. However, existing deep learning methods suffer from high data acquisition costs, low training efficiency, and insufficient generalization capability for boundary conditions. To address these issues, this paper proposes an unsupervised learning method for the wave equation based on finite difference residual constraints. We construct a novel finite difference residual constraint based on structured grids and finite difference methods, as well as an unsupervised training strategy, enabling convolutional neural networks to train without data and predict the forward propagation process of waves. Experimental results show that finite difference residual constraints have advantages over physics-informed neural networks (PINNs) type physical information constraints, such as easier fitting, lower computational costs, and stronger source term generalization capability, making our method more efficient in training and potent in application. Copyright © 2024, The Authors. All rights reserved.

关键词： Finite difference method

High-accurate numerical simulation for Vortex Flow Over a Slender Missile at High Angle of Attack 33

学校读者我要写书评

暂无评论

High-accurate Numerical Simulation for Vortex Flow Over a Sl...

33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022

作者： Gao, Chang-Hao Song, Wen-Ping Han, Shao-Qiang Lu, Kuan Wang, Yue Han, Zhong-Hua Wu, Bin Institute of Aerodynamic and Multidisciplinary Design Optimization National Key Laboratory of Science and Technology on Aerodynamic Design and Research College of Aeronautics Northwestern Polytechnical University Xi’an710072 China Tianfu Engineering-oriented Numerical & Software Innovation Center College of Computer Science Sichuan University Chengdu710071 China Shanghai Electro-mechanical Engineering Institute Shanghai201109 China College of Astronautics Nanjing University of Aeronautics and Astronautics Nanjing211106 China

ISBN: (纸本)9781713871163

Accurate simulation of asymmetrical vortical flow over slender missiles at high angles of attack is crucial for predicting the aerodynamic characteristics of missiles. However, numerical solution for vortices is very sensitive to numerical dissipation. A novel high-order scheme (WENO-K) proposed by our research group can effectively reduce numerical dissipation and capture vortex structures more accurately compared to classical WENO schemes. In this paper, a new numerical method combining 5th WENO-K and IDDES is developed to accurately solve the supersonic unsteady viscous flow dominated by complex asymmetrical vortices over the Sparrow III type missile, and the mechanism of how asymmetrical vortices affect aerodynamic forces of the missile is revealed. © 2022 ICAS. All Rights Reserved.

关键词： Vortex flow

Three-Dimensional numerical Study on the Effect of Radius of the Equal-Area Mixing Chamber on Auxiliary Entraining of the Two-Stage Ejector

学校读者我要写书评

暂无评论

SSRN 2023年

作者： Yan, Jia Gao, Haiping Wang, Zheng School of Civil Engineering and Architecture Southwest University of Science and Technology Mianyang City621010 China Tianfu Engineering Numerical Simulation and Software Innovation Center School of Computer Sciences Sichuan University Chengdu City610041 China

In this study, for the two-stage ejector under three inlet conditions of air-conditioning, refrigerating and freezing, a three-dimensional simulation is used to study the impact of the mixing chamber radius of the first and second stage on the minimum pressure in the ejector without auxiliary entraining first, and then, the impact of real auxiliary entraining effects on ejector performance for two-stage ejector with varied equal-area mixing chamber radius is evaluated accordingly. Results show that: (1) as the second stage equal-area mixing chamber radius (Ram2) increases, the minimum first stage ejector pressure (Pmin1) decreases and the minimum second stage ejector pressure (Pmin2) increases;(2) with the increase of radius of the first-stage equal-area mixing chamber (Ram1), the decreasing effect of Pmin1 and the increasing effect of Pmin2 are both weakened as Ram2 increases from 3.0 mm to 4.6 mm;(3) the minimum pressures of the two-stage have a great influence on the auxiliary entraining effect. © 2023, The Authors. All rights reserved.

关键词： Ejectors (pumps)

Grider-Ho: Rapid and Efficient Parallel software for High-Order Curvilinear Mesh Generation

学校读者我要写书评

暂无评论

SSRN 2024年

作者： Liu, Xiangyu Wang, He Zhao, Zhong Wang, Huadong Guan, Zhidong Wang, Nianhua School of Aeronautic Science and Engineering Beihang University Beijing100191 China Tianfu Engineering-oriented Numerical Simulation & Software Innovation Center Sichuan University Chengdu610207 China State Key Laboratory of Aerodynamics China Aerodynamics Research and Development Center Mianyang621000 China Computational Aerodynamics Institute China Aerodynamics Research and Development Center Mianyang621000 China

The advancement in high-order computational methods is reshaping the landscape of mesh generation in Computational Fluid Dynamics (CFD), steering the focus towards curvilinear mesh techniques to meet the escalating accuracy demands. Grider-HO, a software designed for generating high-order curvilinear mesh efficiently and rapidly, has been developed. It features a layered architecture and utilizes the concurrent hash table and the Alternating Digital Tree (ADT) data structure, supporting thread-level parallelism to convert the straight-edge mesh into the high-order curvilinear mesh seamlessly. Grider-HO initially inserts high-order nodes to a straight-edge mesh using a concurrent hash table, then projects them onto the geometry model with a parallel thread pool. Finally, it employs a localized RBF method with ADT for volume node interpolation, avoiding mesh entanglement. Validated through CFD simulations using the GPU-accelerated PyFR high-order solver, the practicality of Grider-HO is demonstrated across various Reynolds numbers in typical cases like the sphere, the cylinder, and the SD7003 airfoil cases. These results confirm that the high-order curvilinear mesh generated by Grider-HO can meet the high-order requirements of emerging computational methods. Moreover, Grider-HO exemplifies its effectiveness in generating large-scale, high-order curvilinear meshes for DLR-F6 cases. It elevates a 5 million mesh to P2 in 3min39sec at 68% parallel efficiency on 16 threads, and a 14 million mesh to P3 in 52min39sec at 60% parallel efficiency on 16 threads, which illustrates its efficiency and potential in satisfying the demands of complex geometries in engineering applications. © 2024, The Authors. All rights reserved.

关键词： Computational fluid dynamics

A priori subcell limiting based on compact nonuniform nonlinear weighted schemes of high-order CPR method for hyperbolic conservation laws

学校读者我要写书评

暂无评论

arXiv

arXiv 2021年

作者： Zhu, Huajun Liu, Huayong Yan, Zhen-Guo Shi, Guoquan Deng, Xiaogang State Key Laboratory of Aerodynamics Sichuan Mianyang621000 China Tianfu Engineering-Oriented Numerical Simulation & Software Innovation Center Sichuan University Sichuan Chengdu610000 China College of Aerospace Science and Engineering National University of Defense Technology Hunan Changsha410073 China Chinese Academy of Military Science Beijing100071 China

This paper develops a shock capturing approach for high-order correction procedure via reconstruction (CPR) method with Legendre-Gauss solution points. Shock regions are treated by novel compact nonuniform nonlinear weighted (CNNW) schemes, which have the same solution points as the CPR method. CNNW schemes are constructed by discretizing flux derivatives based on Riemann fluxes at flux points in one cell and using nonuniform nonlinear weighted (NNW) interpolations to obtain the left and right values at flux points. Then, a priori subcell p-adaptive CNNW limiting of the CPR method is proposed for hyperbolic conservation laws. Firstly, a troubled cell indicator is used to detect shock regions and to quantify solution smoothness. Secondly, according to the magnitude of the indicator, CNNW schemes with varying accuracy orders are chosen adaptively for the troubled cells. The spectral property and discrete conservation laws are mathematically analyzed. Various numerical experiments show that the CPR method with subcell CNNW limiting has superiority in satisfying discrete conservation laws and in good balance between resolution and shock capturing robustness. Copyright © 2021, The Authors. All rights reserved.

关键词： numerical methods

Finite Volume Graph Network(FVGN): Predicting unsteady incompressible fluid dynamics with finite volume informed neural network

学校读者我要写书评

暂无评论

arXiv

arXiv 2023年

作者： Li, Tianyu Zou, Shufan Chang, Xinghua Zhang, Laiping Deng, Xiaogang School of Computer Science Sichuan University Chengdu610065 China College of Aerospace Science and Engineering National University of Defense Technology Changsha410000 China Unmanned Systems Research Center National Innovation Institute of Defense Technology Beijing100071 China Academy of Military Sciences Beijing100190 China Tianfu Engineering-oriented Numerical Simulation & Software Innovation Center Sichuan University Chengdu610207 China

The rapid development of deep learning has significant implications for the advancement of Computational Fluid Dynamics (CFD). Currently, most pixel-grid-based deep learning methods for flow field prediction exhibit significantly reduced accuracy in predicting boundary layer flows and poor adaptability to geometric shapes. Although Graph Neural Network (GNN) models for unstructured grids based unsteady flow prediction have better geometric adaptability, these models suffer from error accumulation in long-term predictions of unsteady flows. More importantly, fully data-driven models often require extensive training time, greatly limiting the rapid update and iteration speed of deep learning models when facing more complex unsteady flows. Therefore, this paper aims to balance the demands for training overhead and prediction accuracy by integrating physical constraints based on the finite volume method into the loss function of the graph neural network. Additionally, it incorporates a twice-massage aggregation mechanism inspired by the extended stencil method to enhance the unsteady flow prediction accuracy and geometric shape generalization ability of the graph neural network model on unstructured grids. We focus particularly on the model's predictive accuracy within the boundary layer. Compared to fully data-driven methods, our model achieves better predictive accuracy and geometric shape generalization ability in a shorter training time. Copyright © 2023, The Authors. All rights reserved.

关键词： Unsteady flow

Probabilistic Analysis of One-Dimensional Large-Deformation Consolidation Considering Permeability Relationship's Variability

学校读者我要写书评

暂无评论

SSRN 2023年

作者： Li, Duohui Qi, Shunchao Wang, Yuntao Zhou, Jiawen Paul, Simms Yao, Qiang State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Chengdu610065 China College of water resource and hydropower engineering Sichuan University Chengdu610065 China Tianfu Engineering-oriented Numerical Simulation & Software Innovation Center Sichuan University Chengdu610207 China Department of Civil and Environmental Engineering Carleton University OttawaONK1S 5B6 Canada

The large-deformation consolidation theory is fundamental for many applications involving the poromechanical couplings but faces great challenges in making accurate predictions in practices due to significant uncertainties of material permeability,[[EQUATION]]. The permeability could take random values at constant void ratio, [[EQUATION]], due to random microscopic flow channels, moreover, its statistics vary with evolving microscopic structure subjected to volumetric compression during large-deformation consolidation, which is referred to as permeability’s volumetric variability in this work. Current consolidation-related probabilistic models are focused exclusively on the properties’ spatial variability and limited to infinitesimal deformations. Here, we formulate a random large-deformation consolidation model by combining the random field theory with an existing piece-wise linear formulation in the Monte Carlo framework. To embrace volumetric variability, the random field theory is generalized by treating [[EQUATION]] as a dimension-like variable into a non-stationary random field where the statistical moments of [[EQUATION]] changes with [[EQUATION]] (i.e., random [[EQUATION]] relations). To avoid the numeric fluctuations associated with the derivative, [[EQUATION]], we choose the piece-wise linear formulation that directly updates [[EQUATION]] from the generalized random field, which, being different from the conventional random field approach, is performed at every time step since [[EQUATION]] is also a field variable. Hence, the programed model, RANDCON, will simulate the large-deformation consolidation as a random process. The statical results from an example shows that (1) variabilities of [[EQUATION]] yields an overall delayed consolidation due to local clogging, which could be aggravated by the associated fluctuations of [[EQUATION]], (2) "too significant" clogging can, conversely, suppress the clogging by creating a permeable near-surface zone with incre

关键词： Random processes