Evolution of length scales and statistics of Richtmyer-Meshkov instability from direct numerical simulations

In this study we present direct numerical simulation results of the Richtmyer-Meshkov instability (RMI) initiated by $\text{Ma}=1.05,\phantom{\rule{0.16em}{0ex}}\text{Ma}=1.2$, and $\text{Ma}=1.5$ shock waves interacting with a perturbed planar interface between air and $S{F}_{6}$. At the lowest shock Mach number the fluids slowly mix due to viscous diffusion, whereas at the highest shock Mach number the mixing zone becomes turbulent. When a minimum critical Taylor microscale Reynolds number is exceeded, an inertial range spectrum emerges, providing further evidence of transition to turbulence. The scales of turbulent motion, i.e., the Kolmogorov length scale, the Taylor microscale, and the integral length, scale are presented. The separation of these scales is found to increase as the Reynolds number is increased. Turbulence statistics, i.e., the probability density functions of the velocity and its longitudinal and transverse derivatives, show a self-similar decay and thus that turbulence evolving from RMI is not fundamentally different from isotropic turbulence, though nominally being only isotropic and homogeneous in the transverse directions.