Computational analysis of particle-laden flows approaching hypersonic vehicles.

One hazard to the next-generation hypersonic vehicles is hydrometeors including rain, fog, hail, snow, and ice particles which have the potential to cause significant damage to the vehicle structure at hypersonic speeds upon re-entry to the atmosphere. An impact with particles at such high speeds can cause significant/catastrophic damage to the vehicle's surface. Liquid droplets also tend to disintegrate into smaller droplets and create a mist that can further damage the vehicle. In this study, a cloud of solid particles approaching a double-wedge geometry flying at hypersonic speeds is considered to predict the interaction between the shocked flow field and the particles before impact with the hypersonic vehicles’ surface. An Eulerian-Lagrangian, density-based compressible solver is developed to capture the coupling between particles and the high-speed flow field considering a modified Clift-Gauvin particle drag model. A comprehensive statistical analysis of the positions and speed of particles in the range of 1 to 1000 microns is conducted. Probability density functions are generated for particle Mach number, distance, and Weber number along three distinct regions of the shock structure, including the boundary layer, oblique shock, and bow shock. The results show the region behind the oblique shock has a large particle concentration, Mach number, and Weber number. Despite the inlet Mach number being set to 7.0, the post-shock condition surrounding the particles reaches a maximum of Mach 2.5. This is the region more prone to droplet breakup and damage to the surface. This study further provides realistic initial conditions for directing numerical simulation (DNS) of isolated liquid particles that tend to breakup and create smaller droplets.