Richtmyer-Meshkov flows induced by strong shocks

Richtmyer-Meshkov Instability is an instability that develops at the interface between fluids of distinct acoustic impedance when impacted by a shock wave. We study the effect of the adiabatic index of the fluids on the dynamics of strong-shock driven flows, particularly the amount of shock energy available for interfacial mixing. We employ Smooth Particle Hydrodynamics to ensure accurate shock capturing and interface tracking. A range of adiabatic indexes is considered, approaching limits which, to the best of the author's knowledge, have never been considered before. The simulation results are compared wherever possible with rigorous theories, achieving good quantitative and qualitative agreement. We find that the more challenging cases for simulations arise where the adiabatic indexes are further apart, and that the initial growth rate is a non-monotone function of the initial perturbation amplitude, which holds across all adiabatic indexes of the fluids considered. We also find that the velocity of the transmitted shock depends on the initial perturbation amplitude, and this dependence is non-monotone. The empiric models are elaborated to decribe our results achieveing excellent agreement with data. The applications of these findings on experiment design are discussed.