Simulations of three-layer Richtmyer-Meshkov mixing in a shock tube*

The Richtmyer-Meshkov instability causes perturbations to grow after a shock traverses a fluid density interface. This increases the mixing rate between fluid from either side of the interface. We use the Flash Eulerian hydrodynamic code to investigate alterations when a thin third layer of intermediate density is placed along the interface, effectively creating two adjacent unstable interfaces. This is a common occurrence in engineering applications where a thin barrier initially separates two materials. We find that the width of the mixing layer is similar or slightly reduced, however the total mass of mixed material can actually increase for high Atwood number cases.The relative phase of the perturbations makes a significant difference to the fluids' late-time evolution. The Flash results are also benchmarked against two-layer experimental data from a shock tube at the University of Arizona.