Explosive dispersal of solid particles

Abstract

The rapid dispersal of inert solid particles due to the detonation of a heterogeneous explosive, consisting of a packed bed of steel beads saturated with a liquid explosive, has been investigated experimentally and numerically. Detonation of the spherical charge generates a blast wave followed by a complex supersonic gas-solid flow in which, in some cases, the beads catch up to and penetrate the leading shock front. The interplay between the particle dynamics and the blast wave propagation was investigated experimentally as a function of the particle size (100-925 µm) and charge diameter (8.9-21.2 cm) with flash X-ray radiography and blast wave instrumentation. The flow topology during the dispersal process ranges from a dense granular flow to a dilute gas-solid flow. Difficulties in the modeling of the high-speed gas-solid flow are discussed, and a heuristic model for the equation of state for the solid flow is developed. This model is incorporated into the Eulerian two-phase fluid model of Baer and Nunziato (1986) and simulations are carried out. The results of this investigation indicate that the crossing of the particles through the shock front strongly depends on the charge geometry, the charge size and the material density of the particles. Moreover, there exists a particle size limit below which the particles cannot penetrate the shock for the range of charge sizes considered. Above this limit, the distance required for the particles to overtake the shock is not very sensitive to the particle size but remains sensitive to the particle material density. Overall, excellent agreement was observed between the experimental and computational results.

Effect of a bimodal initial particle volume fraction perturbation in an explosive dispersal of particles

“…The origin of these aerodynamically stable structures is an active research topic. These particulate jets, as seen in experiments by Frost [1,2], could be due to a wide variety of complex physics and their interplay. These physics include (i) interactions between the blast-wave structure and the cloud of particles, (ii) compaction and break-up phenomena and (iii) multiphase flow instabilities.…”

Turbulent mixing and afterburn in post-detonation flow with dense particle clouds

“…Such explosives are primarily designed to enhance the afterburn in the post-detonation flow field. Past studies of afterburn [1,2,3,4,5] have attempted to quantify the evolution of the blast wave and the mixing zone behind it, but these studies are mostly limited to explosives with a low volume fraction of solid particles, i.e., < 0.01. However, experimental and realistic high energy heterogeneous explosives contain a large number of particles with the range of volume fraction of particles between 0.01 to 0.65.…”

Interaction of a planar shock with a dense field of particles

“…Gas-solid flows are characterized by the particle volume fraction φ p of the flow [1]. If the particle volume fraction is less than about 0.1%, flow is considered 'dusty,' or dilute, and particle collisions are not important [2].…”