An extension of detonation shock dynamics for Insensitive Explosives

Resolved, direct numerical simulations of the detonation of high explosives (HE) in geometries of engineering interest are largely unattainable due to the scale disparity between the shorter detonation reaction-zone length and the longer characteristic explosive charge dimension. However, multi-scale mathematical modeling, utilizing this scale disparity, has led to the development of the theory of detonation shock dynamics (or DSD). With DSD, the propagation of a detonation in a HE configuration is described by a surface evolution equation for the detonation front. For insensitive high explosives (IHE), detonations typically have two characteristic reaction stages: a fast reaction where the majority of the heat of reaction is released, followed by a second significantly slower reaction (e.g. through carbon coagulation in PBX-9502). We show that the presence of this slowly reacting, weak heat release zone can have a significant (time-dependent) influence on the evolution of a detonation in IHE. We also describe an extension to the DSD concept, specifically tailored to detonations in IHE, which treats fast-slow chemistry models. The fast chemistry is handled with a DSD front rationally coupled to a distributed, resolved (reactive burn) model for handling the slow chemistry step.