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A High Order Positivity-Preserving Discontinuous Galerkin Remapping Method Based on a Moving Mesh Solver for ALE Simulation of the Compressible Fluid Flow

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Communications in computational Physics 2023年第10期34卷 1177-1214页

作者： Xiaolu Gu Juan Cheng Chi-Wang Shu Graduate School China Academy of Engineering PhysicsBeijing 100088China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China Division of Applied Mathematics Brown UniversityProvidenceRI 02912

The arbitrary Lagrangian-Eulerian(ALE)method is widely used in the field of compressible multi-material and multi-phase flow *** order to implement the indirect ALE approach for the simulation of compressible flow in the context of high order discontinuous Galerkin(DG)discretizations,we present a high order positivity-preserving DG remapping method based on a moving mesh solver in this *** remapping method is based on the ALE-DG method developed by Klingenberg et al.[17,18]to solve the trivial equation∂u/∂t=0 on a moving mesh,which is the old mesh before remapping at t=0 and is the new mesh after remapping at t=*** appropriate selection of the final pseudo-time T can always satisfy the relatively mild smoothness requirement(Lipschitz continuity)on the mesh movement velocity,which guarantees the high order accuracy of the remapping *** use a multi-resolution weighted essentially non-oscillatory(WENO)limiter which can keep the essentially non-oscillatory property near strong discontinuities while maintaining high order accuracy in smooth *** further employ an effective linear scaling limiter to preserve the positivity of the relevant physical variables without sacrificing conservation and the original high order *** experiments are provided to illustrate the high order accuracy,essentially non-oscillatory performance and positivity-preserving of our remapping *** addition,the performance of the ALE simulation based on the DG framework with our remapping algorithm is examined in one-and two-dimensional Euler equations.

关键词： Remapping discontinuous Galerkin method arbitrary Lagrangian-Eulerian high order accuracy multi-resolution WENO limiter positivity-preserving

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Numerical study on micro-fracture mechanism of rock dynamic failureinduced by abrupt unloading under high in-situ stresses

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Theoretical & applied Mechanics Letters 2024年第6期14卷 486-495页

作者： Yuezong Yang Anye Li Zhushan Shao Kui Wu Wei Wei Wenhui Du Yujie Wang School of Science Xi’an University of Architecture and TechnologyXi’an 710055China CAEP Software Center for High Performance Numerical Simulation Institute of Applied Physics and Computational Mathematics BeijingBeijing 100088China

Rock burst is a kind of severe engineering disaster resulted from dynamic fracture process of *** macrofailure behaviors of rocks are primarily formed after experiencing the initiation,propagation,and coalescenceof *** this paper,the grain-based discretized virtual internal bond model is employed to investigatethe fracturing process of unloaded rock under high in-situ stresses from the micro-fracture *** micro-fracturing process reveals that the longitudinal stress waves induced by unloading lead to thevisible unloading *** influences of in-situ stresses,mineral grain sizes,and grain heterogeneity on rockmacro and micro fracture are ***-crack areas of tensile and shear cracks and micro-crack anglesare statistically analyzed to reveal the rock micro-fracture *** simulated results indicate thatthe combined effect of the stress state transition and the unloading effect dominates the rock unloading *** vertical and horizontal in-situ stresses determine the stress state of surrounding rock after unloading andthe unloading effect,*** the vertical stress increases,the stress level after unloading is higher,andthe shear failure characteristics become more *** the horizontal stress increases,the unloading effectincreases,leading to the intensification of tensile *** mineral grain size and grain heterogeneity alsohave nonnegligible influences on rock unloading *** micro-fracture perspective provides further insightinto the unloading failure mechanism of deep rock excavation.

关键词： Rock burst Micro-fracture Dynamic failure Unloading effect

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Dual-Primal Isogeometric Tearing and Interconnecting Methods for the Stokes Problem 13th

Dual-Primal Isogeometric Tearing and Interconnecting Methods...

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13th International Conference on Spectral and High Order Methods, ICOSAHOM 2021

作者： Sogn, Jarle Takacs, Stefan Johann Radon Institute for Computational and Applied Mathematics Austrian Academy of Sciences Linz Austria Institute of Computational Mathematics Johannes Kepler University Linz Linz Austria

ISBN: (纸本)9783031204319

We are interested in a fast solver for linear systems obtained by discretizing the Stokes problem with multi-patch Isogeometric Analysis. We use Dual-Primal Isogeometric Tearing and Interconnecting (IETI-DP) methods. In resent years, IETI-DP and related methods have been studied extensively, mainly for the Poisson problem. For the Stokes equations, several challenges arise since the corresponding system is not positive definite, but has saddle point structure. Moreover, the Stokes equations with Dirichlet boundary conditions have a null-space, consisting of the constant pressure modes. This poses a challenge when considering the scaled Dirichlet preconditioner. We test out two different scaled Dirichlet preconditioners with different choices of primal degrees of freedom. The tests are performed on rather simple domains (the unit square and a quarter annulus) and a more complicated domain (a Yeti-footprint). © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Linear systems

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Numerical study of the influence of interfaces between explosives and steel plates

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Shock Waves 2025年 1-13页

作者： Liu, J. Sun, Z. Y. Yin, J. W. Zhang, F. G. Institute of Applied Physics and Computational Mathematics Beijing China

The interface between explosives and steel plates can vary in the clearance of a gap or the presence of a cushion, and the dimension of the interface region can also differ. These variations in the types of interface may affect the dynamic loading and energy absorption of steel plates driven by detonation. To investigate this issue, we conducted a numerical study on the influence of different interface types and thicknesses. Initially, we designed a simulation model of a detonation driving a steel plate, with one half featuring clearance between the explosive and the steel, and the other half filled with a cushion. We then carried out simulations to analyze the influence of varying clearance and cushion thickness on the dynamic loading and energy absorption of the steel plate. The results indicate that a small-thickness clearance between explosive and steel can increase the kinetic energy of the steel plate, and there may be an optimal clearance thickness to maximize the energy absorption of the steel plate. As the clearance thickness is increased, the first loading pressure in the steel decreases, and the spallation and recompression processes in the steel gradually transform into an approximately uniform loading process without fracture. On the other hand, filling the clearance with a cushion has a negative effect on the energy absorption of the steel plate, and the kinetic energy of the steel plate decreases nearly linearly with an increase of the cushion thickness. As the cushion thickness is increased, the first loading pressure in the steel decreases less, and the dynamic behaviors of spallation and recompression may occur. Lastly, we briefly discuss interfaces with uneven thickness, which should be strictly controlled to prevent the occurrence of unexpected phenomena.

关键词： Detonation-driven plate Explosive-metal interface Gap clearance Energy absorption

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Stability and Instability of Schwarzschild-AdS for the Nonlinear Einstein-Klein-Gordon System

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Acta Mathematicae Applicatae Sinica 2022年第4期38卷 778-812页

作者： Feng-Xia LIU Bo-Ling GUO Institute of Artificial Intelligence Beihang UniversityBeijing 100083China Institute of Applied Physics and Computational Mathematics Beijing 100088China

In this paper,we study the global behavior of solutions to the spherically symmetric(it means that the problem is 2+2 framework)coupled Nonlinear-Einstein-Klein-Gordon(NLEKG)system in the presence of a negative cosmological *** prove the well posedness of the NLEKG system in the Schwarzschild-AdS spacetimes and that the Schwarzschild-AdS spacetimes(the trivial black hole solutions of the EKG system for whichφ=0 identically)are asymptotically *** perturbations of Schwarzschild-AdS initial data again lead to regular black holes,with the metric on the black hole exterior approaching a SchwarzschildAdS *** argument on the black hole exterior,with the redshift effect and weighted Hardy inequalities playing the fundamental role in the *** integrated decay and pointwise decay estimates are obtained.

关键词： nonlinear-Einstein-Klein-Gordon equation schwarzschild-AdS spacetime well-posedness bootstrap

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Reconstructing the Absorption Function in a Quasi-Linear Sorption Dynamic Model via an Iterative Regularizing Algorithm

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Advances in applied mathematics and Mechanics 2024年第1期16卷 237-252页

作者： Alexey Shcheglov Jingzhi Li Chao Wang Alexander Ilin Ye Zhang Faculty of Computational Mathematics and Cybernetics Shenzhen MSU-BIT UniversityShenzhenGuangdong 518172China Faculty of Computational Mathematics and Cybernetics Lomonosov Moscow State UniversityMoscowRussia Department of Mathematics&National Center for Applied Mathematics Shenzhen&SUSTech International Center for Mathematics Southern University of Science and TechnologyShenzhenGuangdong 518055China School of Mathematics and Statistics Beijing Institute of TechnologyBeijing 100081China

This study addresses the parameter identification problem in a system of time-dependent quasi-linear partial differential equations(PDEs).Using the integral equation method,we prove the uniqueness of the inverse problem in nonlinear ***,using the method of successive approximations,we develop a novel iterative algorithm to estimate sorption *** stability results of the algorithm are proven under both a priori and a posteriori stopping rules.A numerical example is given to show the efficiency and robustness of the proposed new approach.

关键词： Inverse problem quasi-linear dynamic model uniqueness method of successive approximations stability

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Influences of chemical reactions on polysulfide reduction reaction process on promotor surface in Li-S batteries

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Nano Research 2024年第4期17卷 2712-2718页

作者： Yufeng Luo Zhenhan Fang Zixin Hong Shaorong Duan Haitao Liu Hengcai Wu Qunqing Li Yuegang Zhang Shoushan Fan Wenhui Duan Jiaping Wang Tsinghua-Foxconn Nanotechnology Research Center Tsinghua UniversityBeijing 100084China Department of Physics Tsinghua UniversityBeijing 100084China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Frontier Science Center for Quantum Information Tsinghua UniversityBeijing 100084China

Polar promotors have been proven effective in catalyzing the polysulfide(PS)reduction reaction(PSRR)process in lithium-sulfur(Li-S)***,the promotor surface tends to be poisoned due to the accumulation of insoluble discharging products of lithium disulfide(Li_(2)S_(2))and lithium sulfide(Li_(2)S)during Li-S battery ***,we investigate the detailed PSRR mechanism on the surface of manganese sulfides(MnS)as a representative promoter by performing in-situ Raman mapping *** catalytic ability of MnS enables thorough electrochemical reduction of PSs to Li_(2)S_(2) and Li_(2)S on the MnS *** generated Li_(2)S_(2) and Li_(2)S then adsorb the dissolved PSs via chemical reactions among sulfur species during the subsequent PSRR *** phenomenon mitigates promotor poisoning and continuously improves the reversible ***,the assembled Li-S cell demonstrates excellent electrochemical performance after introducing a conductive interlayer containing a thin piece of carbon nanotube film and MnS promotors.

关键词： promotors polysulfides chemical reactions catalytic ability in-situ Raman measurements

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Numerical Analysis of Transient Electromagnetic Responses in Cuboidal Cavities Exposed to X-ray Radiation

Numerical Analysis of Transient Electromagnetic Responses in...

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2024 Photonics and Electromagnetics Research Symposium, PIERS 2024

作者： Meng, X. Li, G. Zhang, L. Caep Software Center for High Performance Numerical Simulation China Institute of Applied Physics and Computational Mathematics China

ISBN: (纸本)9798350375909

Internal Electromagnetic Pulse (IEMP) generated inside a cavity, known as Cavity IEMP, would disrupt the operational integrity of embedded electronic systems upon exposure to transient X-ray radiation. In this paper, we employ a coupled approach, integrating the Monte Carlo Method with a 3D Electromagnetic Particle-in-Cell (PIC) Method, to quantify IEMP responses in a cuboidal cavity. The Monte Carlo simulation addresses the interactions between the wall materials and X-rays, yielding detailed energy and angular spectra of electrons produced on both the upper and lower walls of a cavity. Additionally, a proposed 3D electromagnetic particle-in-cell method is used to simulate the self-consistent evolution of the electromagnetic fields generated inside the cavity, driven by the electrons induced by X-ray exposure. With such a method, transient electromagnetic fields inside a cuboidal cavity exposed to X-rays are calculated and analyzed. This research contributes to the advancement of radiation-hardened design strategies for electronic systems, particularly in spacecraft applications. © 2024 IEEE.

关键词： Electromagnetic transients

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HYBRID REGULARIZED CONE-BEAM RECONSTRUCTION FOR AXIALLY SYMMETRIC OBJECT TOMOGRAPHY

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Acta Mathematica Scientia 2022年第1期42卷 403-419页

作者： Xinge LI Suhua WEI Haibo XU Chong CHEN Institute of Applied Physics and Computational Mathematics Beijing 100094China LSEC ICMSECAcademy of Mathematics and Systems ScienceCASBeijing 100190China

In this paper,we consider 3 D tomographic reconstruction for axially symmetric objects from a single radiograph formed by cone-beam *** contemporary density reconstruction methods in high-energy X-ray radiography are based on the assumption that the cone beam can be treated as fan beams located at parallel planes perpendicular to the symmetric axis,so that the density of the whole object can be recovered layer by *** the relationship between different layers,we undertake the cone-beam global reconstruction to solve the ambiguity effect at the material interfaces of the reconstruction *** view of the anisotropy of classical discrete total variations,a new discretization of total variation which yields sharp edges and has better isotropy is introduced in our reconstruction ***,considering that the object density consists of continually changing parts and jumps,a high-order regularization term is *** final hybrid regularization model is solved using the alternating proximal gradient method,which was recently applied in image *** reconstruction results are presented for simulated radiographs,which shows that the proposed method has led to an improvement in terms of the preservation of edge location.

关键词： high-energy X-ray radiography cone-beam global reconstruction inverse problem total variation alternating proximal gradient method

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An Improved Hybrid Method for Solving Large-Scale Electromagnetic Problems with Local Inhomogeneous Structures

An Improved Hybrid Method for Solving Large-Scale Electromag...

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2023 International applied computational Electromagnetics Society Symposium, ACES-China 2023

作者： Liu, Yang Wang, Chao-Fu Wu, Wen-Bin Zhou, Hai-Jing Institute of Applied Physics and Computational Mathematics Beijing China National University of Singapore Singapore

ISBN: (纸本)9781733509657

An iterative FEBI-PO hybrid method has been proposed to deal with the large-scale problem having local inhomogeneous structures. In this paper, the PEC part of exterior surface of inhomogeneous structure is also taken as PO region, which makes the PO region as large as possible. Moreover, in the iterative process, only the problem with the variables on the dielectric boundary of local complex inhomogeneous structure and the problem with variables in PO region need to be solved alternately, which avoids solving the whole problem in FEBI region repeatedly. In addition, several numerical results are discussed to illuminate the efficiency of the improved scheme. © 2023 applied computational Electromagnetics Society (ACES).

关键词： Physical optics

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