Molecular dynamics simulation of cylindrical Richtmyer-Meshkov instability

作     者：Zhenhong Wu Shenghong Huang Juchun Ding Weirong Wang Xisheng Luo 

作者机构：Department of Modern Mechanics University of Science and Technology of China 

出 版 物：《Science China(Physics,Mechanics & Astronomy)》 (中国科学：物理学、力学、天文学（英文版）)

年 卷 期：2018年第61卷第11期

页      面：61-71页

核心收录：

学科分类：07[理学] 070203[理学-原子与分子物理] 0702[理学-物理学] 

基　　金：supported by the China Postdoctoral Science Foundation(Grant No.2016M602026) the National Natural Science Foundation of China(Grant Nos.11625211,and 11621202) the Science Challenge Project(Grant No.TZ2016001) the Fundamental Research Funds for the Central Universities 

主　　题：molecular dynamics simulation Richtmyer-Meshkov instability converging shock 

摘      要：The microscopic-scale Richtmyer-Meshkov(RM) instability of a single-mode Cu-He interface subjected to a cylindrically converging shock is studied through the classical molecular dynamics simulation. An unperturbed interface is first considered to examine the flow features in the convergent geometry, and notable distortions at the circular inhomogeneity are observed due to the atomic fluctuation. Detailed processes of the shock propagation and interface deformation for the single-mode interface impacted by a converging shock are clearly captured. Different from the macroscopic-scale situation, the intense molecular thermal motions in the present microscale flow introduce massive small wavelength perturbations at the single-mode interface, which later significantly impede the formation of the roll-up structure. Influences of the initial conditions including the initial amplitude,wave number and density ratio on the instability growth are carefully analyzed. It is found that the late-stage instability development for interfaces with a large perturbation does not depend on its initial amplitude any more. Surprisingly, as the wave number increases from 8 to 12, the growth rate after the reshock drops gradually. The distinct behaviors induced by the amplitude and wave number increments indicate that the present microscopic RM instability cannot be simply characterized by the amplitude over wavelength ratio(η). The pressure history at the convergence center shows that the first pressure peak caused by the shock focusing is insensitive to η, while the second one depends heavily on it.