Formation of unburnt pockets in gaseous detonations

Formation of unburnt pockets in gaseous detonations is caused by two mechanisms: longitudinal and transverse mechanisms. The longitudinal mechanism is based on longitudinal instability of the detonation front. In the transverse mechanism, interactions between transverse waves lead to the formation of unburnt pockets. In this paper, the transverse mechanism is investigated via two-dimensional numerical simulations of propagation of gaseous detonation in a channel. A front structure that includes triple points, transverse waves, the incident shock, and the Mach stem is formed, as the detonation propagates in the channel. The origin of unburnt pockets is explained by the interaction between transverse waves or corresponding triple points that detach a portion of the reactant from the detonation front. It is observed that the size of the unburnt pockets and the depth of penetration to the products increase with increasing activation energy and that the shape of the pockets also changes with activation energy.