  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).
