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.

Detonation propagation in a condensed explosive with metal particles can result in signi cant momentum transfer between the explosive and the particles during their crossing of the leading shock front. Consequently, the assumption of a`phaseinteraction-frozen shock' used in multiphase continuum models for detonation initiation and propagation may not be valid. This paper addresses this issue by performing numerical and theoretical calculations in liquid explosives and RDX with various compressible metal particles under conditions of detonation pressure. The results show that the momentum transferred to heavy-metal particles such as tungsten is not signi cant after the shock{particle interaction. However, light-metal particles including aluminium, beryllium and magnesium rapidly accelerate during the shock{ particle interaction. They reach a considerable speed immediately behind the shock front, typically 60{100% of the ®ow speed of the explosive. It is important to take this signi cant momentum transfer at the shock front into account when modelling the shock initiation and detonation structure for two-phase mixtures of condensed explosive and light-metal particles.

No abstract

No abstract

No abstract