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.

Freeze-out of perturbation growth for shocked heavy fluid layers by eliminating reverberating waves

“…After the shock impact, phase reversal generally arises at the second interface of the heavy fluid layer (Meyer & Blewett 1972). Previous fluid-layer studies have indicated that, once phase reversal of the second interface is accomplished, the spike continually grows downstream so that freeze-out cannot be achieved by the interface coupling (Liang et al 2020;Cong et al 2022). Consequently, the freeze-out for the second interface needs to be achieved before phase reversal.…”

“…This leads to the model's inability to correctly characterize the parameters required for freeze-out. Second, reverberating waves within the layer continually interact with fluid-layer interfaces, resulting in additional Rayleigh-Taylor effects and stretching effects (Liang et al 2020;Cong et al 2022), thereby causing the freeze-out theory of Mikaelian (1995) to be invalid. In other words, the presence of reverberating waves makes it difficult to achieve freeze-out for fluid-layer interfaces by interface coupling alone since, even if the interface coupling leads to freeze-out of perturbation growth, the reverberating waves would destroy the freeze-out state.…”

“…In this work, freeze-out for a heavy fluid layer is investigated both theoretically and numerically. The heavy fluid layer has been a commonly considered configuration in previous studies, and the evolution mechanism for this type of fluid layer has been extensively studied (Jacobs et al 1993(Jacobs et al , 1995Balakumar et al 2008Balakumar et al , 2012Balasubramanian, Orlicz & Prestridge 2013;Orlicz et al 2015;Liang et al 2020;Cong et al 2022). Nevertheless, exploration involving freeze-out of perturbation growth for the heavy fluid layer is limited (Mikaelian 1995(Mikaelian , 1996.…”

Interfacial instabilities driven by co-directional rarefaction and shock waves

“…The interfacial instability driven by successive shocks/rarefactions or rarefactions/shocks is more complex than that caused by a single wave. Previous studies, involving reshock-interface interactions (Hill, Pantano & Pullin 2006;Lombardini et al 2011;Li et al 2019Li et al , 2021 and fluid-layer behaviours (Liang & Luo 2021;Cong et al 2022), have primarily focused on the interfacial instabilities induced by different waves. In these studies, the constraints imposed by rigid walls or fluid-layer interfaces cause shocks and rarefactions to bounce back and forth, resulting in repeated interactions with the interface.…”

“…2019, 2021) and fluid-layer behaviours (Liang & Luo 2021; Cong et al. 2022), have primarily focused on the interfacial instabilities induced by different waves. In these studies, the constraints imposed by rigid walls or fluid-layer interfaces cause shocks and rarefactions to bounce back and forth, resulting in repeated interactions with the interface.…”