Computational simulation of detonation initiation in heterogenous explosives

Abstract

Two different modeling strategies are employed to examine aspects of detonation dynamics in heterogeneous, condensed-phase explosives by means of accurate and well-resolved numerical computations. The first model applies at the macroscale and treats the explosive as a two-phase continuum of reactant and product. Balance laws of mass, momentum and energy are supplemented by constitutive relations in the form of equations of state and reaction rate. A parametric study of inert compaction waves and detonations is undertaken for both idealized and realistic constitutive choices. Of special interest is the behavior of the run-to-detonation distance as a function of the initial porosity of the explosive. It is found that this response can vary qualitatively depending upon the constitutive input to the model. For up-to-date equation-of-state and reaction-rate information it is found that the response is in agreement with recent experimental results, and mechanisms responsible for this response are identified. The second model couples the macroscale to the mesoscale, the scale of the explosive grains. Continuum models for both the scales are proposed: a compressible, reactive flow with compaction at the macroscale and a reaction-diffusion system at the mesoscale. A parametric study is undertaken to examine the role of hot spots, which are sites of elevated temperature and/or pressure at the mesoscale, in detonation initiation.