Evaporation Effects in Shock-Driven Multiphase Instabilities

This paper considers the effects of multiphase parameters on a shock-driven particle-laden hydrodynamic instability using simulations performed with the hydrocode FLAG, developed at Los Alamos National Laboratory. The classic sinusoidal interface common in instability literature is created using water particles seeded in a nitrogen–water vapor mixture. The simulations model a shock tube environment as the computational domain, to guide future experimentation. Multiphase physics in FLAG include momentum and energy coupling, with this paper discussing the addition of mass coupling through evaporation. The multiphase effects are compared to a dusty gas approximation, which ignores multiphase components, as well as to a multiphase case which ignores evaporation. Evaporation is then further explored by artificially changing parameters which effect the rate of evaporation as well as the amount of total evaporation. Among all these experiments, the driving force of the hydrodynamic instability is a shock wave with a Mach number of 1.5 and a system Atwood number of 0.11 across the interface. The analysis is continued into late time for select cases to highlight the effects of evaporation during complex accelerations, presented here as a reshock phenomenon. It was found that evaporation increases the circulation over nonevaporating particles postshock. Evaporation was also shown to change the postshock Atwood number. Reshock showed that the multiphase instabilities exhibited additional circulation deposition over the dusty gas approximation. Mixing measures were found to be affected by evaporation, with the most significant effects occurring after reshock.