密度扰动的类Richtmyer-Meshkov不稳定性增长及其与无扰动界面耦合的数值模拟  

Numerical simulation study on growth of Richtmyer-Meshkov-like instability of density perturbation and its coupling with unperturbed interfaces

作　　者：孙贝贝 叶文华[2] 张维岩[2] Sun Bei-Bei;Ye Wen-Hua;Zhang Wei-Yan(Graduate School,China Academy of Engineering Physics,Beijing 100088,China;Institute of Applied Physics and Computational Mathematics,Beijing 100094,China)

机构地区：[1]中国工程物理研究院研究生院,北京100088 [2]北京应用物理与计算数学研究所,北京100094

出　　处：《物理学报》2023年第19期135-142,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11675026,11575033)资助的课题。

摘　　要：靶丸材料内部扰动在冲击波作用后会产生类似Richtmyer-Meshkov(RM)不稳定性的增长并耦合到烧蚀面产生扰动种子.本文使用数值模拟的方法研究了这种类RM不稳定性增长规律以及不稳定性与界面的耦合机制.研究表明,线性阶段密度扰动类RM不稳定性增长速度满足δv∝k_(y)△uη.密度扰动到界面的耦合有声波耦合和涡合并两种机制,声波耦合引起的界面扰动增长速度满足δ_(v i)/(k_(y)△uη)∝e^(-k_(y)L).界面上的Atwood数为正时,界面上涡量和密度扰动的涡量方向相同,涡合并导致扰动速度增大.Atwood数为正时,降低界面上的Atwood数以及增大界面上过渡层的宽度均可减小密度扰动耦合引起的界面扰动增长.The interaction between the shock and the internal density perturbation of the target material produces a Richtmyer-Meshkov-like(RM-like)instability,which couples with the ablation front and generates instability seeds.Recent studies have demonstrated the significance of internal material density perturbations to implosion performance.This paper presents a two-dimensional numerical investigation of the growth of the RM-like instability in linear region and its coupling mechanism with the interface.Euler equations in two dimensions are solved in Cartesian coordinates by using the fifth-order WENO scheme in space and the two-step Runge-Kutta scheme in time.The computational domain has a length of 200μm in the x-direction andλ_(y)in the y-direction.The numerical resolution adopted in this paper isΔ_(x)=Δ_(y)=y/128.A periodic boundary condition is used in the y-direction,while an outflow boundary condition is used in the x-direction.The interaction between shock and density perturbation will deposit vorticity in the density perturbation region.The width of the density perturbation region can be represented by the width of the vortex pair.The growth rate of the RM-like instability can be represented by the growth rate of the width of the density-disturbed region or the maximum perturbation velocity in the y-direction.The simulation results show that the growth rate of the vortex pair width is proportional to the perturbation wave number k_(y),the perturbation amplitude h,and the velocity difference before and after the shock wave△_(u),specifically,δv∝k_(y)△uη.In the problem of coupling the RM-like instability with the interface,we calculate the derivation of the interface perturbation amplitude with respect to time to obtain the growth rate of the interface.It is concluded from the simulations that the coupling of the RM-like instability with the interface has two mechanisms:acoustic coupling and vortex merging.When the density perturbation region is far from the interface,only acoustic wave is coupled wit

关 键 词：惯性约束聚变 密度不均匀 类Richtmyer-Meshkov不稳定性 扰动种子 

分 类 号：TL632[核科学技术—核技术及应用]