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Please wait a minute... For Selected: Download Citations EndNote Ris BibTeX Toggle Thumbnails Select 3D Lagrangian Methods for Ideal Magnetohydrodynamics on Unstructured Meshes XU Xiao, GAO Zhiming, DAI Zihuan CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2020, 37 (4): 403-412.   Abstract （374）   HTML （6）    PDF （8849KB）（1054）       Knowledge map    Interaction between magnetic field and fluids is crucial in Z pinch process. Since Z pinch involves with multi materials and severe deformation, we develop 3D compatible Lagrangian staggered and cell-centered schemes for ideal MHD on unstructured meshes. Both of the schemes are of first order in space and time discretization. Accuracy and robustness of the schemes are validated with typical numerical tests. Reference | Related Articles | Metrics Select Investigation of Normal Shock Structure by Using Navier-Stokes Equations with the Second Viscosity LI Xindong, ZHAO Yingkui, HU Zongmin, JIANG Zonglin CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2020, 37 (5): 505-513.   DOI: 10.19596/j.cnki.1001-246x.8121 Abstract （361）   HTML （8）    PDF （2299KB）（1383）       Knowledge map    To investigate influence mechanism of the second viscosity on internal flow of a normal shock wave, one-dimensional Navier-Stokes equations are numerically solved. It indicates that the second viscosity has a smoothing effect on density, heat flow and energy distribution in the shock wave, which results in a decrease of peak value of heat and entropy flows, and an increase of shock thickness. Due to the production of normal viscous dissipation, some lost mechanical energy is converted into internal energy. As considering the second viscosity, density distribution and shock thickness are greatly improved. They are in good agreement with experimental data. In addition, Knudsen number is obtained 0.12≤Kn≤0.4 within Mach number range from 1.2 to 10. It indicates that Navier-Stokes equations with the second viscosity simulate normal shock structure more accurately. Reference | Related Articles | Metrics Select A Godunov Method with Staggered Lagrangian Discretization Applicable to Isentropic Flows SUN Chen, LI Xiao, SHEN Zhijun CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2020, 37 (5): 529-538.   DOI: 10.19596/j.cnki.1001-246x.8144 Abstract （332）   HTML （3）    PDF （4941KB）（1229）       Knowledge map    In cell-centered Godunov method,unphysical overheating problem exists in rarefaction flows.We develop a Godunov method with staggered Lagrangian discretization which is applicable to isentropic flows. Velocity and thermodynamic variables are defined in staggered discretization. The velocity averaging process in a cell is avoided,so that the kinetic energy dissipation due to the momentum averaging process is removed. In contrast to the traditional von Neumann staggered grid method, the face flux is provided by a node multidimensional Riemann solver. The difficulty in selecting multidimensional artificial viscosity is overcome. In order to reduce unphysical entropy production of multidimensional Riemann solver in rarefaction problems,we give a reasonable criterion of rarefaction appearance to satisfy the thermodynamic relation. Numerical results show that the method removes overheating problem in rarefaction problems, and retains the property of accurate shock capturing of the original Lagrangian Godunov method as well. Reference | Related Articles | Metrics Select Numerical Simulation of One-dimensional Elastic-Perfectly Plastic Flow and Suppression of Wall Heating Phenomenon LI Xiao, SUN Chen, SHEN Zhijun CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2020, 37 (5): 539-550.   DOI: 10.19596/j.cnki.1001-246x.8141 Abstract （418）   HTML （3）    PDF （3643KB）（1225）       Knowledge map    An HLLC-type approximate Riemann solver is proposed to simulate one-dimensional elastic-perfectly plastic flow with Wilkins model. This Riemann solver introduces plastic wave and has the same wave number with actual physics. The wave speed is determined by characteristic analysis of wave system. The algorithm is simple to implement and does not need iteration. In order to reduce wall heating error in the simulation for strong shock (or rarefaction), wall heating viscosity is designed to effectively suppress the non-physical wall heating phenomenon. Reference | Related Articles | Metrics Select First-principles Study of Hydrogen Behaviors in Plutonium Oxides ZHANG Le, SUN Bo, SONG Haifeng CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2020, 37 (5): 595-602.   DOI: 10.19596/j.cnki.1001-246x.8118 Abstract （340）   HTML （2）    PDF （9461KB）（1403）       Knowledge map    In-depth investigation of hydrogen behaviors in Pu-oxide overlayers (mainly PuO2 and α-Pu2O3) is critical for modeling complex induction period of Pu hydriding. Within DFT+U and DFT-D3 schemes, systematic first-principles calculations and ab initio thermodynamic evaluations reveal that hydrogen absorption, dissolution behaviors, and diffusion mechanism in PuO2 are quite different from those in α-Pu2O3, among which highly endothermic absorption and dissolution of hydrogen are primary hydrogen resistance mechanism of PuO2. Since its difficult recombination, atomic H is preferred existence state in PuO2, but H will recombine spontaneously in α-Pu2O3. In PuO2, H diffusion is always clinging to O anions, whereas in α-Pu2O3, H2 prefers to migrate along O vacancies with higher barriers. Based on a series of theoretical studies, we conclude that the main interactions between hydrogen and Pu-oxide overlayers are not involved with chemical reactions and intact PuO2 can effectively inhibit hydrogen permeation.The hydrogen dissolution in α-Pu2O3 can be reasonably described by an ideal solid solution model. Reference | Related Articles | Metrics