Numerical study of Richtmyer–Meshkov instability of light fluid layer with reshock

Abstract

The Richtmyer–Meshkov instability of a light fluid layer driven by reflected shock is investigated numerically and theoretically to reveal the feature of the interfacial evolution of light fluid layer under reshock. Cases with single- and double-perturbation helium gas layers are investigated to study the evolution and merging of interface, and comparisons with diverse layer thicknesses and initial perturbation amplitude are conducted to explore the coupling effects of the interface. For the single-perturbed case, the amplitude variation of the left interface exhibits a distinct inflection point as impacted by the reflected shock, and the growth rate in the reflected stage is noticeably larger than that in the incident stage. During the merging process of the interfaces, the displacement difference between the two interfaces and the amplitude growth of the interface play a dominant role before and after the reshock, respectively. For the double-perturbed cases, the head-on collision of the two interfaces' spike occurs when the two interfaces are initially anti-phase, and the spike “catching up with” the bubble occurs when the two interfaces are initially in phase. While the initial fluid layer is very thin, the merging of interfaces accelerates and the interface-coupling effect increases. A modified model has been proposed to predict the amplitude growth of the interface after reshock, which agrees well with the numerical results. The distribution and development of vorticity are similar for the studied cases with different initial amplitudes and fluid layer thicknesses.