Experimental Investigation of the effects of Mach number and initial condition on mixing transition in shock-driven flow*

Effects of initial condition and incident shock strength (Mach number) on the Richtmyer-Meshkov instability (RMI) evolution are presented here. The interface between light (N₂) and heavy (CO₂) gases is inclined with respect to shock propagation by 10 degrees (amplitude to wavelength ratio of 0.088), which forms the predominantly single-mode perturbation. A perturbed, multi-mode inclined interface is also created via shear-buoyancy induced roll-ups between the two gases superposed on the dominant inclined mode. These two interface conditions are accelerated by planar shock waves of M≈1.55 and M≈1.9 to investigate the RMI development and mixing transition in this flow. Ensemble-averaged turbulence statistics are computed using simultaneous planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) measurements at two times after incident shock and two times after reshock. The observations from turbulent kinetic energy spectra and mixing Reynolds number indicate that the criteria for mixing transition can be satisfied at late time after the incident shock for the multi-mode case at higher Mach number, and after reshock for both Mach numbers and both initial conditions.