Numerical study of oblique detonation initiations with chain branching kinetics

Oblique detonations induced by semi-infinite wedge are simulated by solving Euler equations with chain branching kinetics. Numerical results show the initiation can be triggered by either the abrupt transition or smooth transition, dependent on incident Ma M_in and wedge angle θ, and then their effects on the oblique detonation angle β and initiation length L_ini are analyzed. When θ increases, L_ini decreases monotonically but β has a minimum value, corresponding to θ = 29° in this study. When Min decreases, both L_ini and β increases monotonically until M_in decreases below certain critical value, M_in = 9.2 in this study. Then low inflow Ma effects generate the maximum L_ini, with the complex of ODW (oblique detonation wave), SODW (secondary oblique detonation wave) and SIDW (self-ignition deflagration wave). The transient process is observed, demonstrating the structure can self-adjust to find a proper position. The wave structure suggests two wave/heat release process determining the detonation initiation. In the cases with high M_in featured by SIDW, the oblique-shock induced self-ignition dominates, and L_ini increases when M_in decreases. In the cases with low M_in featured by SODW, the interaction of ODW and SODW dominates, and L_ini decreases when Min decreases.