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Theoretical investigations on x-ray transport in radiation transport experiments on the Shenguang-Ⅲ prototype laser facility

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Matter and Radiation at Extremes 2022年第2期7卷 25-32页

作者： Guangwei Meng Jun She Tianming Song Jiamin Yang Min Wang Institute of Applied Physics and Computational Mathematics P.O.Box 8009Beijing 100088People’s Republic of China Research Center of Laser Fusion Mianyang 621900People’s Republic of China

Experiments exploring the propagation of heat waves within cylindrical CH foams were performed on the Shenguang-Ⅲ prototype laser facility in *** this paper,the radiation fluxes out of CH foam cylinders at different angles are analyzed theoretically using the two-dimensional radiation hydrodynamics code *** to the difficulty in validating opacity and equation of state(EOS)data for high-Z plasmas,and to uncertainties in the measured radiation temperature Tr and the original foam densityρ0,multipliers are introduced to adjust the Au material parameters,Tr,andρ0 in our simulations to better explain the *** dependences of the peak radiation flux Fmax and the breakout time of the heat wave thalf(defined as the time corresponding to the radiation flux at half-maximum)on the radiation source,opacity,EOS,andρ0 scaling factors(η_(src),η_(op),η_(eos),and η_(ρ))are investigated via numerical simulations combined with ***,with the uncertainties in the measured Tr andρ0 fixed at 3.6%and 3.1%,respectively,experimental data are exploited as fiducial values to determine the ranges ofη_(op) andη*** is found that the ranges ofη_(op) andηeos fixed by this experiment overlap partially with those found in our previous work[Meng et al.,*** 20,092704(2013)].Based on the scaled opacity and EOS parameters,the values of F_(max) and t_(half) obtained via simulations are in good agreement with the measurements,with maximum errors∼9.5%and within 100 ps,respectively.

关键词： cylindrical overlap adjust

Kinetics of Rayleigh-Taylor instability in van der Waals fluid: the influence of compressibility

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arXiv 2024年

作者： Chen, Jie Xu, Aiguo Zhang, Yudong Chen, Dawei Chen, Zhihua National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing210094 China National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics P. O. Box 8009-26 Beijing100088 China State Key Laboratory of Explosion Science and Safety Protection Beijing Institute of Technology Beijing100081 China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China National Key Laboratory of Shock Wave and Detonation Physics Mianyang621999 China School of Mechanics and Safety Engineering Zhengzhou University Zhengzhou450001 China

Early studies on Rayleigh-Taylor instability (RTI) primarily relied on the Navier-Stokes (NS) model. As research progresses, it becomes increasingly evident that the kinetic information that the NS model failed to capture is of great value for identifying and even controlling the RTI process;simultaneously, the lack of analysis techniques for complex physical fields results in a significant waste of data information. In addition, early RTI studies mainly focused on the incompressible case and the weakly compressible case. In the case of strong compressibility, the density of the fluid from the upper layer (originally heavy fluid) may become smaller than that of the surround- ing (originally light) fluid, thus invalidating the early method of distinguishing light and heavy fluids based on density. In this paper, tracer particles are incorporated into a single-fluid discrete Boltzmann method (DBM) model that considers the van der Waals potential. By using tracer par- ticles to label the matter-particle sources, a careful study of the matter-mixing and energy-mixing processes of the RTI evolution is realized in the single-fluid framework. The effects of compress- ibility on the evolution of RTI are examined mainly through the analysis of bubble and spike velocities, the ratio of area occupied by heavy fluid, and various entropy generation rates of the system. It is demonstrated that: (i) compressibility has a suppressive effect on the spike velocity, and this suppressive impact diminishes as the Atwood number (At) increases. The influence of compressibility on bubble velocity shows a staged behavior with increasing At. (ii) The impact of compressibility on the entropy production rate associated with the heat flow ( SNOEF ) is related to the stages of RTI evolution. Moreover, this staged impact of compressibility on SNOEF varies with At. Compressibility exhibits an inhibitory effect on the entropy production rate associated with viscous stresses ( SNOMF). (iii) By incor

关键词： Compressibility

Approximating reproduction numbers: a general numerical method for age-structured models

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arXiv 2023年

作者： De Reggi, Simone Scarabel, Francesca Vermiglio, Rossana CDLAb - Computational Dynamics Laboratory University of Udine Italy Department of Mathematics Computer Science and Physics University of Udine Italy Department of Applied Mathematics University of Leeds United Kingdom

In this paper, we introduce a general numerical method to approximate the reproduction numbers of a large class of multi-group, age-structured, population models with a finite age span. To provide complete flexibility in the definition of the birth and transition processes, we propose an equivalent formulation for the age-integrated state within the extended space framework. Then, we discretize the birth and transition operators via pseudospectral collocation. We discuss applications to epidemic models with continuous and piecewise continuous rates, with different interpretations of the age variable (e.g., demographic age, infection age and disease age) and the transmission terms (e.g., horizontal and vertical transmission). The tests illustrate that the method can compute different reproduction numbers, including the basic and type reproduction numbers as special *** Codes 34L16, 37N25, 65L15, 65L60, 65P99, 92D25, 92D30 Copyright © 2023, The Authors. All rights reserved.

关键词： Numerical methods

Uniform Anisotropic Regularity and Low Mach Number Limit of Non-isentropic Ideal MHD Equations with a Perfectly Conducting Boundary

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arXiv 2024年

作者： Ju, Qiangchang Wang, Jiawei Zhang, Junyan Institute of Applied Physics and Computational Mathematics Beijing China Hua Loo-Keng Center for Mathematical Sciences Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing China Department of Mathematics National University of Singapore Singapore

We prove the low Mach number limit of non-isentropic ideal magnetohydrodynamic (MHD) equations with general initial data in the half-space whose boundary satisfies the perfectly conducting wall condition. By observing a special structure contributed by Lorentz force in vorticity analysis, we establish uniform estimates in suitable anisotropic Sobolev spaces with weights of Mach number determined by the number of material derivatives. We also observe that the entropy has the enhanced regularity in the direction of the magnetic field. These two observations help us get rid of the loss of derivatives and weights of Mach number in vorticity analysis caused by the simultaneous appearance of entropy, general initial data and the magnetic field, which is one of the major difficulties that do not appear in Euler equations or the isentropic problems. By utilizing the technique of Alinhac good unknowns, the anti-symmetric structure is preserved in the tangential estimates for the system differenetiated by high-order material derivatives. © 2024, CC BY.

关键词： Euler equations

Stability and related zero viscosity limit of steady plane Poiseuille-Couette flows with no-slip boundary condtion

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arXiv 2022年

作者： Jiang, Song Zhou, Chunhui Department of Mathematics Southeast University Nanjing210096 China Institute of Applied Physics and Computational Mathematics Beijing China

We prove the existence and stability of smooth solutions to the steady Navier-Stokes equations near plane Poiseuille-Couette flow. Consequently, we also provide the zero viscosity limit of the 2D steady Navier-Stokes equations to the steady Euler equations. First, in the absence of any external force, we prove that there exist smooth solutions to the steady Navier-Stokes equations which are stable under infinitesimal perturbations of plane Poiseuille-Couette flow. In particular, if the basic flow is the Couette flow, then we can prove that the flow is stable for any finite perturbation o(1). Moreover, we also show that for any smooth shear flow satisfying (1.27), if we put a proper external force to control the flow, then we can also obtain a smooth solution of the steady Navier-Stokes equations which is stable for infinitesimal perturbation of the external force. Finally, based on the same linear estimates, we establish the zero viscosity limit of all the solutions obtained above to the solutions of the Euler equations. © 2022, CC BY.

关键词： Shear flow

Scaling Laws Governing the Elastic Properties of 3D-Graphenes

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arXiv 2024年

作者： Li, Ming Lu, Guo Yu, Haodong Li, Menglei Zheng, Fawei School of Physics Beijing Institute of Technology Beijing100081 China Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing100081 China LCP Institute of Applied Physics and Computational Mathematics Beijing100088 China Department of Physics Capital Normal University Beijing100048 China

In this study, we have comprehensively investigated the scaling law for elastic properties of three-dimensional honeycomb-like graphenes (3D-graphenes) using hybrid neural network potential based molecular dynamics simulations and theoretical analyses. The elastic constants as functions of honeycomb hole size, denoted by the graphene wall length L, were provided. All five independent elastic constants in the large L limit are proportional to L−1. The associated coefficients are combinations of two-dimensional graphene’s elastic constants. High-order terms including L−2 and L−3 emerge for finite L values. They have three origins, the distorted areas close to the joint lines of 3D-graphenes, the variation of solid angles between graphene plates, and the bending distortion of graphene plates. Significantly, the chirality becomes essential with the decreasing of L, because the joint line structures are different between the armchair and zigzag type 3D-graphenes. Our findings provide insights into the elastic properties of graphene-based superstructures and can be used for further studies on graphene-based materials. Copyright © 2024, The Authors. All rights reserved.

关键词： Graphene

Data-Driven Prediction of Complex Crystal Structures of Dense Lithium

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arXiv 2023年

作者： Wang, Xiaoyang Wang, Zhenyu Gao, Pengyue Zhang, Chengqian Lv, Jian Wang, Han Liu, Haifeng Wang, Yanchao Ma, Yanming State Key Laboratory of Superhard Materials International Center for Computational Method and Software College of Physics Jilin University Changchun130012 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Fenghao East Road 2 Beijing100094 China DP Technology Beijing100080 China College of Engineering Peking University Beijing100871 China HEDPS CAPT College of Engineering Peking University Beijing100871 China

Lithium (Li) is a prototypical simple metal at ambient conditions, but exhibits remarkable changes in structural and electronic properties under compression. There has been intense debate about the structure of dense Li, and recent experiments offered fresh evidence for new yet undetermined crystalline phases near the enigmatic melting minimum region in the pressure-temperature phase diagram of Li. Here, we report on an extensive exploration of the energy landscape of Li using an advanced crystal structure search method combined with a machine learning approach, which greatly expands the scale of structure search, leading to the prediction of four complex Li crystal phases containing up to 192 atoms in the unit cell that are energetically competitive with known Li structures. These findings provide a viable solution to the newly observed yet unidentified crystalline phases of Li, and showcase the predictive power of the global structure search method for discovering complex crystal structures in conjunction with accurate machine-learning potentials. Copyright © 2023, The Authors. All rights reserved.

关键词： Lithium

FOURIER DECAY OF FRACTAL MEASURES ON SURFACES OF CO-DIMENSION TWO IN R5

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arXiv 2023年

作者： Cao, Zhenbin Miao, Changxing Wang, Zijian Institute of Mathematics Henan Academy of Sciences Zhengzhou450046 China Institute of Applied Physics and Computational Mathematics Beijing100088 China Zhongkai University of Agriculture and Engineering Guangzhou510225 China

In this paper, we study the Fourier decay of fractal measures on the quadratic surfaces of high co-dimensions. Unlike the case of co-dimension 1, quadratic surfaces of high co-dimensions possess some special scaling structures and degenerate characteristics. We will adopt the strategy from Du and Zhang [22], combined with the broad-narrow analysis with different dimensions as divisions, to obtain a few lower bounds of Fourier decay of fractal measures on quadratic surfaces of co-dimension two in R5 Copyright © 2023, The Authors. All rights reserved.

关键词： Fractal dimension

Uncertainty analysis of experiment and numerical simulation of spallation 30

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Uncertainty analysis of experiment and numerical simulation ...

30th European Safety and Reliability Conference, ESREL 2020 and 15th Probabilistic Safety Assessment and Management Conference, PSAM15 2020

作者： Zheng, Miao Wei, Lan Institute of Applied Physics and Computational Mathematics Beijing China

ISBN: (纸本)9789811485930

When the metal material undergoes a series of physical processes such as strong impact loading, unloading, reverse stretching and reloading in the complex system, the spallation of the material is easy to occur in the reverse stretching stage. In order to study the movement behavior and law of metal materials under strong impact loading, the free surface particle velocity and the movement process of the sample surface with time were obtained by the combined measurements of VISAR (velocity interferometer system for any reflector) and electric probe technique. In this paper, the uncertainty sources of two kinds of systems are analyzed, and the test error ranges are given respectively. In the two-dimensional Lagrange hydrodynamics program, we have added the hole fracture growth, polymerization and collapse effect of spallation processing function, and verify the model and program code through a numerical example. In the comparison between the experimental results and the calculated results, the width of the platform area and the takeoff height of the speed curve are in good agreement, and the relative error is less than 10%. In order to verify the reliability of numerical simulation, the research on the test method of grid independence and time independence is carried out. The influence of grid number and time step on the platform width in velocity curve is analyzed, and the determination method of grid number and time step is discussed. © ESREL2020-PSAM15 *** by Research Publishing, Singapore.

关键词： Probes