Triple point shear-layers in gaseous detonation waves

Abstract

Recent experiments have shown intriguing regions of intense luminescence or "hot spots" in the vicinity of triple point shear-layers in propagating gaseous detonation waves. Localized explosions have also been observed to develop in these fronts. These features were observed in higher effective activation energy mixtures, but not in lower effective activation energy mixtures. We investigate the possibility that the increased lead shock oscillation through a cell cycle in higher activation energy mixtures may result in a significantly increased disparity in the induction time on either side on the triple point shear-layer, increasing the probability that shear-layer instability may develop between reacted and unreacted gas streams. We carry out two-dimensional simulations with detailed chemical kinetics to examine the nature of the triple point shear-layer in three mixtures with different effective activation energy. In the low activation energy mixture, large scale vortical structures are observed to occur downstream of the ignition distance; these structures do not have a noticeable effect on the reaction. In higher effective activation energy mixtures, a transverse ignition front develops near the interface between the two gas streams and results in a rapidly propagating reaction front. The transverse ignition front develops due to molecular diffusion across the shear-layer between hot and cold gas streams.

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