A numerical study of detonation diffraction

Abstract

An investigation of detonation diffraction through an abrupt area change has been carried out via a set of two-dimensional numerical simulations parameterized by the activation energy of the reactant. Our analysis is specialized to a reactive mixture with a perfect gas equation of state and a single-step reaction in the Arrhenius form. Lagrangian particles are injected into the flow as a diagnostic tool for identifying the dominant terms in the equation that describes the temperature rate of change of a fluid element, expressed in the shock-based reference system. When simplified, this equation provides insight into the competition between the energy release rate and the expansion rate behind the diffracting front. The mechanism of spontaneous generation of transverse waves along the diffracting front is carefully analysed and related to the sensitivity of the reaction rate to temperature. We study in detail three highly resolved cases of detonation diffraction that illustrate different types of behaviour, super-, sub-and near-critical diffraction.

A study of detonation diffraction in the ignition-and-growth model

“…To our knowledge diffraction computations for condensed explosives at such high resolution have not appeared in the literature. In the gaseous phase, however, high-resolution diffraction computations do exist; see, in particular, Arienti and Shepherd [15]. Our results are obtained for a rigid confinement of the explosive.…”

Oblique detonation waves stabilized in rectangular-cross-section bent tubes

“…Shepherd [32]) is similar to that from bent tubes if an initial pressure of detonable mixture is sufficiently low, and inside-wall curvature radius is sufficiently large, but such diffracted detonation wave propagation is not always steady state. We focused on the stabilized detonation wave which could occur when the super critical condition was satisfied (an initial pressure of detonable mixture is sufficiently high, and inside-wall curvature radius is sufficiently small).…”

A multi-material flow solver for high speed compressible flows

“…This high-resolution grid enables to capture the physics of the problem including bubble breakup as shown in Figure 22. The various instances leading to the final collapse of the bubble are highlighted using Schlieren-like relative density variations [35]. These images accentuate the various features such as shock reflection using density gradients.…”

“…These images accentuate the various features such as shock reflection using density gradients. The formula used to compute the Schlieren function,  , which is graphically represented, [35] is max 0.8*exp ,…”