High-Amplitude Single-Mode Perturbation Evolution at the Richtmyer-Meshkov Instability

The single-mode Richtmyer-Meshkov hydrodynamic instability at light/heavy (air/SF₆ and air/CO₂), close density (air/N₂), and heavy/light (air/He) interfaces has been experimentally studied for a low incident shock wave Mach number. Two identical 2D half sinusoidal initial perturbations, with a relatively high initial amplitude, were considered in order to rapidly reach the nonlinear regime and check the reduction of the initial growth rate compared to that predicted by the small-amplitude theory. The growth rate measurements for the air/SF₆ and air/CO₂ cases are in excellent agreement with the nonlinear model of Sadot et al. coupled with a reduction factor suggested by Rikanati et al. In the air/N₂ case, the reversal phase can be precisely described by the linear theory. Finally, the heavy/light experiment is well described by the Vandenboomgaerde model also coupled with a smaller reduction factor.