Numerical Simulation of Transition to Detonation in a Hydrogen-air Mixture Due to Shock Wave Focusing on a 90-Deg Wedge

The interaction of a shock wave with a specific angle or concave wall due to its reflection and focusing is a way to onset the detonation provided sufficiently strong shock wave. In this work, we present numerical simulation results of the detonation initiation due to the shock reflection and focusing in a 90-degree wedge for mixtures of H2 and air. The code used was ddtFoam [1–3] that is a component of the larger OpenFOAM open-source CFD package of density-based code for solving the unsteady, compressible Navier-Stokes equations. The numerical model represents the 2-D geometry of the experiments performed by Rudy [4]. The numerical results revealed three potential scenarios in the corner after reflection: shock wave reflection without ignition, deflagrative ignition with intermediate transient regimes with a delayed transition to detonation in lagging combustion zone at around 1.8 mm from the apex of the wedge, and ignition with an instantaneous transition to detonation with the formation of the detonation wave in the corner tip. In the experimental investigation, the transition velocity for the stoichiometric mixture was approximately 715 m/s, while in the numerical simulation, the transition velocity for the stoichiometric mixture was 675.65 m/s, 5.5% decrease in velocity.