Flow Instability: Richtmyer-Meshkov and Pulsating Flows

Experiments on the Richtmyer-Meshkov Instability (RMI) in two- and three-layer configurations are presented. Two light-over-heavy two-layer cases are considered, one utilizing air as the light gas and sulfur hexafluoride (SF₆) as the heavy gas, and the second utilizing carbon dioxide (CO₂) as the light gas and SF₆ as the heavy gas. Two additional three-layer cases are considered in a light-intermediate-heavy configuration. The first case utilizes helium (He) as the light gas, air as the intermediate gas, and SF₆ as the heavy gas, and the second case utilizes air as the light gas, CO₂ as the intermediate gas, and SF₆ as the heavy gas. Interfaces between each layer are formed using the counterflow technique of Jones & Jacobs (Phys. Fluids, 9 (10) 1997), thus producing initally stable, stratified, membraneless interfaces in both the two- and three-layer cases. The gas column is vertically oscillated using a voice coil actuator, resulting in a random, multi-modal Faraday wave perturbation being imposed on the heavy-light interface in the two-layer case, and the intermediate-heavy interface in the three-layer case. A shock wave with a nominal Mach number of M=1.2 in the light gas travels downwards towards the interface region, initiating the RMI. Comparisons of the growth of the mixing layer width between the cases are presented. Additional comparisons with previous multi-layered RMI experiments with single mode perturbations are also presented to assess the influence of the multi-modal perturbations.