Large-amplitude effects on interface perturbation growth in Richtmyer–Meshkov flows with reshock

Abstract

Experimental and theoretical studies on the Richtmyer–Meshkov (RM) instability of heavy/light gaseous interfaces with reshock are performed. Both small and large initial perturbation amplitudes of single- and quasi-single-mode interfaces are considered, highlighting the effects of interface amplitude and shape on the linear and nonlinear growths of the RM instability. The results indicate that for small-amplitude interfaces distorted before and after the first reshock arrival, the perturbation growths at linear stages can be well predicted by the impulsive model. For large-amplitude interfaces, however, the reshock acceleration on the evolving interface promotes the mode interaction and enhances the nonlinear effects, making the perturbation growth rates reduced in comparison with those in the singly shocked cases. The complete evolution, especially the bubble evolution, has a strong memory of initial shapes, while for large-amplitude cases, the spike evolution is nearly independent of them owing to the destruction of large-scale vortices and multiple-shock-induced small-scale structures. Compared with that of the single-mode case, the normalized perturbation growths after reshock for the quasi-single-mode cases are more sensitive to initial amplitudes. To better describe the linear growth rates of the RM instability induced by the incident shock and reshock, the reduction factor models for large-amplitude cases are developed, which successfully predict the non-monotonic dependence of linear growth rates on initial perturbation amplitudes. For small-amplitude cases, the nonlinear model proposed for the singly shocked case can predict the reshocked nonlinear growth, while for large-amplitude cases, it is invalid because the perturbation growth shows a linear characteristic after reshock.