Numerical study of shock driven multiphase systems with reactions

Abstract

This work details the analysis of the shock-driven multiphase instability (SDMI) of a gas-particle system and implementation of reaction model for multiphase detonation simulation. 3D numerical simulations were carried out for the study of SDMI. Two cases, one with an evaporating particle (water) cloud and another with a gas only approximation were run in the hydrodynamics code FLASH. Both cases had an incident Mach number of 1.65 and an effective Atwood number of 0.046. It is shown that both the gas hydrodynamics and particle properties influence one another and are coupled. This coupling causes lag, clustering, and evaporation in particles. The gas only approximation, a classical Richtmyer-Meshkov instability, cannot replicate those effects from particles and thus, qualitative and quantitative differences in its evolution and that of shock-driven multiphase instability are seen. The dusty gas shows much faster evolution and larger vorticity deposition compared to the particles case. Coupling between the interface hydrodynamic evolution and particle evaporation is further explored by examination of the multiphase case. Hydrodynamic driven particle clustering is measured through particle spatial distribution statistics and particle-vorticity correlations. It is found that the small particles quickly form vorticity driven small scale clusters while hydrodynamics act to reorganize the particles into larger scale features at later times. Particle evaporation rates are found to vary greatly, even among similar sizes, and show poor agreement with 1D evaporation model. The role of hydrodynamic organization in evaporation is shown by examining the spatial distribution of variations in evaporation rate. Small to medium sized particles initially located at the outside of the sphere, in the equatorial region (taking the sphere to have poles aligned with the shock transit direction) are most affected by the hydrodynamic development and show higher evaporation rates, similar to those found with a 1D, one-way coupled, single particle evaporation model. The induction time parameter model was implemented in FLASH and gaseous and multiphase detonations are simulated. The results of 1D gaseous simulation are in good agreement with previous results. The results of 1D multiphase simulation of JP10-O2 shows that the large sized particles take more time to achieve self-sustaining detonation and have larger induction zone. However, no significant drop in peak pressure and velocity is seen for the particle sizes (diameter [less than or equal to] 15 [mu]m) simulated.