Numerical simulation of detonation reignition in H $_2$-O $_2$ mixtures in area expansions

Abstract. Time-dependent, two-dimensional, numerical simulations of a transmitted detonation show reignition occuring by one of two mechanisms. The first mechanism involves the collision of triple points as they expand along a decaying shock front. In the second mechanism ignition results from the coalescence of a number of small, relatively high pressure regions left over from the decay of weakened transverse waves. The simulations were performed using an improved chemical kinetic model for stoichiometric H $_2$-O $_2$ mixtures. The initial conditions were a propagating, two-dimensional detonation resolved enough to show transverse wave structure. The calculations provide clarification of the reignition mechanism seen in previous H $_2$-O $_{2}$-Ar simulations, and again demonstrate that the transverse wave structure of the detonation front is critical to the reignition process.