Vorticity Suppression by Particle Lag Effects in Shock-Driven Multiphase Instability

Abstract: Shock-driven multiphase mixing occurs in many physical systems such as explosive dispersal of chemical or biological agents, in the evolution of supernova remnants, and in supersonic and detonative combustion engines. This mixing process is driven by the Shock Driven Multiphase Instability (SDMI), a derivative of the canonical Richtmyer-Meshkov Instability (RMI). The SDMI deviates from the RMI as particle lag effects become significant, where a higher momentum deficit leads to longer equilibration times and a reduction in hydrodynamic mixing. In this work, the effect of particle lag (rate of momentum transfer) on the SDMI evolution was isolated and investigated utilizing solid nondeforming and nonevaporating particles of differing sizes while holding the effective density ratio (mass of particles in the interface) constant. Three particle sizes were selected with increasing velocity relaxation times. Experiments were conducted by accelerating a cylindrical interface comprised of air and seeded particles surrounded by clean (particle-free) air with a Mach 1.35 shock wave. The development of the multiphase interface was measured using particle imaging velocimetry (PIV). Circulation measurements showed a decrease in mixing with increasing particle size. Finally, a new model, derived from theory, is proposed to predict circulation deposition, mixing energy, in the SDMI based on shock strength, effective density ratio, and particle response times.