Instability growth patterns of a shock-accelerated thin fluid layer

Laser-induced fluorescence imaging of a shock-accelerated thin gas layer, produced by a planar ${\mathrm{SF}}_6$ jet in air, shows multiple flow evolutions. Richtmyer-Meshkov instability causes spatially periodic perturbations initially imposed on the jet to develop into one of three distinct flow patterns, indicating nonlinear instability growth. Slight differences in the vorticity distribution deposited on the air-${\mathrm{SF}}_6$ interfaces by the shock interaction produce a bifurcated flow, observed as mushroom-shaped or sinuous-shaped interfacial patterns.