The effect of collisions on the explosive dispersal of particles

Abstract

The explosive dispersal of particles produces distinct clusters or jets of particles within the expanding flow. The mechanism that precipitates this behavior is still not fully understood. Experimental data at the particle level can be difficult to obtain, as experiments often involve explosive testing. Simulations may offer additional insight into how the jetting phenomenon develops. A series of 2D simulations are performed in order to investigate the phenomenon at the mesoscale, with fully resolved particle–particle and particle–gas interactions. Particles are modeled as fully resolved cylinders via a volume penalization method. Phase interactions are captured by two-way particle–gas coupling and particle–particle collisions and momentum transfer. Two particle cloud geometries are considered in order to isolate possible sources of jetting: planar shock and compression waves impacting a rectangular particle cloud and an annular cloud about a cylindrically expanding blast wave. In each case, particle distribution within the cloud is varied with forced initial perturbations in area fraction in order to investigate the effects of spatial perturbation on cloud development. Particle positions, velocities, acceleration, and spatial auto-correlation statistics are used to characterize the evolution of the system over time. Jetting is observed to be mainly influenced by particle collisions as opposed to fluid interactions due to the time scale in which fluid structures take to form.