Vortex morphology in Richtmyer–Meshkov-induced turbulent mixing

This study investigates the vortical structures that form and develop during the turbulent mixing induced by the Richtmyer–Meshkov instability (RMI). By using high-resolution implicit large-eddy simulations, we examine the turbulent structures that develop post-shock at a planar interface separating two distinct gases and track their evolution in time during subsequent reshocks and rarefactions. Although no coherent turbulent structures can be identified during the early phase of the mixing process following the initial shock at the interface, further deposition of baroclinic vorticity caused by subsequent reshocks and rarefactions leads to the formation of various coherent turbulent structures. At late time, when the two fluids become heavily mixed at the molecular level and the mixing width becomes sufficiently large, the coherent structures eventually break down to form very fine isotropic turbulent structures that exhibit no obvious structure or shape. The study also considers shock interactions with an inclined interface, such as an inverse chevron interface, where several additional coherent structures form independently of the RMI — these are due instead to the initial geometric inclination of the interface itself. Finally, we discuss the importance of the formation of such structures in the modelling of RMI-type mixing processes and draw several important conclusions.