Particle Jet Formation During Explosive Dispersal

TL;DR

This study investigates the formation of particle jets during explosive dispersal, analyzing how different materials and conditions influence jet number and stability, with implications for understanding shock-induced particle behavior.

Contribution

It provides experimental insights into particle jet formation mechanisms and compares effects of different dispersal media and saturation levels.

Findings

Water dispersal produces more jets than dry powder but with quicker dissipation.

Saturated particle beds generate more jets than dry or water-only dispersals.

Particle size, density, and explosive-to-particle ratio affect jet formation susceptibility.

Abstract

Previous experimental studies have shown that when a layer of solid particles is explosively dispersed, the particles often develop a non-uniform spatial distribution. The instabilities within the particle bed and at the particle layer interface likely form on the timescale of the shock propagation through the particles. The mesoscale perturbations are manifested at later times in experiments by the formation of coherent clusters of particles or jet-like particle structures, which are aerodynamically stable. A number of different mechanisms likely contribute to the jet formation including shock fracturing of the particle bed and particle-particle interactions in the early stages of the dense gas-particle flow. Aerodynamic wake effects at later times contribute to maintaining the stability of the jets. The experiments shown in this fluid dynamics video were carried out in either spherical or cylindrical geometry and illustrate the formation of particle jets during the explosive dispersal process. The number of jet-like structures that are generated during the dispersal of a dry powder bed is compared with the number formed during the dispersal of the same volume of water. The liquid dispersal generates a larger number of jets, but they fragment and dissipate sooner. When the particle bed is saturated with water and explosively dispersed, the number of particle jets formed is larger than both the dry powder and pure water charges. More extensive experiments that explore the effect of particle size, density and the mass ratio of explosive to particles on the susceptibility for jet formation are reported in Frost et al. (Proc. of 23rd ICDERS, Irvine, CA, 2011).