Experimental and theoretical studies on heavy fluid layers with reshock

Abstract

The Richtmyer–Meshkov instability of a heavy fluid layer with reshock is investigated experimentally and theoretically, to reveal the mechanisms of the interfacial instabilities and motions of waves and interfaces under reshock conditions. Three kinds of heavy fluid layers with different thicknesses in unperturbed and perturbed cases are considered, highlighting the effects of initial layer thickness on the interface evolution. A general one-dimensional theory for describing the interaction between unperturbed interfaces and waves under reshock conditions is constructed, which supports the instability analysis and theoretical modeling in the perturbed cases. The perturbed fluid-layer results indicate that as the fluid-layer thickness decreases, the inhibition of squeezing effects on perturbation growth is gradually stronger than the promotion of rarefaction-wave effects on perturbation growth. The whole mixing width of fluid layers after reshock acceleration exhibits an approximately linear growth feature, and the reshocked mixing width growth rate is weakly dependent on the initial layer thickness, which is different from the finding before reshock. The linear amplitude growth of the right interface after reshock is promoted by the interface coupling effects but is still smaller than the prediction of the empirical linear model. When the squeezing effects are weak, the nonlinear model, which considers the modification of rarefaction-wave effects, can well predict the perturbation growth during and after the acceleration stage of rarefaction waves.