Particle momentum effects from the detonation of heterogeneous explosives

Abstract

Detonation of a spherical high explosive charge containing solid particles generates a high-speed two-phase flow comprised of a decaying spherical air blast wave together with a rapidly expanding cloud of particles. The particle momentum effects associated with this two-phase flow have been investigated experimentally and numerically for a heterogeneous explosive consisting of a packed bed of inert particles saturated with a liquid explosive. Experimentally, the dispersion of the particles was tracked using flash radiography and high-speed photography. A particle streak gauge was developed to measure the rate of arrival of the particles at various locations. Using a cantilever gauge and a free-piston impulse gauge, it was found that the particle momentum flux provided the primary contribution of the multiphase flow to the near-field impulse applied to a nearby small structure. The qualitative features of the interaction between a particle and the flow field are illustrated using simple models for the particle motion and blast wave dynamics. A more realistic Eulerian two-fluid model for the gas-particle flow and a finite-element model for the structural response of the cantilever gauge are then used to determine the relative contributions of the gas and particles to the loading.

Numerical Modeling of Heterogeneous High Explosives

“…There are no abnormally hot particles near the core using the Figures 16 and 17 show trajectory plots along with the data from the Frost experiment. 6 In this case, the Friedman blast wave solution produces less accurate results than the Taylor blast wave solution. Here, the shock wave propagates far too quickly at the beginning of the simulation and thus propels the particles to an unusually high velocity.…”

“…12,13 In 2007, Frost performed experiments which tracked the explosive clouds created by the detonation of a heterogeneous mixture of Nitromethane and steel particles. 6,7 The Frost study will provide a basis to compare the numeric simulation to experimental data. The purpose of this study is to construct and analyze a numeric algorithm based on theoretical methods which can accurately model the detonation and two-phase flow of a heterogeneous high explosive.…”

Explosive fragmentation of liquids in spherical geometry

“…The explosive shock wave causes the thin-walled glass casing to fracture into very fine fragments which are carried out by the gas flow behind the shock. Previous work [8] has shown that these glass fragments are visible on flash X-ray radiographs taken during the explosive dispersal of solid particles. While the fracture of the glass into fine fragments could generate fine-scale perturbations at the liquid interface, the size of the glass fragments appears to be much less than the spacing of the subsequent liquid jets.…”

Heterogeneous/particle-laden blast waves

“…Embedding inert particles within an explosive or surrounding the explosive with a layer of particles or liquid generally leads to a mitigation in the blast overpressure and impulse, at least in the near field, with a corresponding transfer of kinetic energy to the particles or liquid [8]. As a result of the significant momentum flux associated with the particles, the complex gas-particle flow that is generated may impart a significant impulsive loading on nearby structures or personnel [9]. The experimental and numerical investigation of the properties of such particleladen flows with blast waves is the subject of this thematic issue.…”