Interaction of Detonations with Supersonic Obstacles

Abstract The motion of a driven obstacle moving at supersonic speeds in a reactant mixture leads to a complex flow field consisting of shocks and turbulent flow structures with non-uniform reactant distribution. The interaction of the strongest form of a reaction wave, a detonation, with such a flow field begins with detonation-shock interactions, and is followed sequentially by complex shock reflections, detonation diffraction, and detonation-turbulence interactions. The boundary and initial conditions at the end of each interaction sets the stage for the next interaction. The purpose of this paper is to understand how the detonation wave is affected by this interaction. A parametric study is performed to study the effects of chemical heat release, obstacle size, and speed on the detonation dynamics. First, we compared the interaction of a detonation and a non-reacting shock with the moving obstacle. We found that the non-reacting shock was affected over a longer distance on interacting with the obstacle. Then, we varied the obstacle height and speed to understand how it affects the intrinsic cellular structure of the detonation wave. We found that the detonation fully quenched due to diffraction when the obstacle height was larger than the detonation cell size for a given obstacle speed. An analysis of the detonation wave based on the Damköhler number characterizes how the detonation dynamics are affected by the interaction when the obstacle speed is varied for a fixed obstacle height. We found that the interaction has the overall effect of reducing the Damköhler number at the detonation front. The distribution of reactants and the local flow field surrounding the obstacle have a major influence on the detonation dynamics.