Abstract

Wedge-induced oblique detonation waves (ODWs) have been studied widely, but their interactions with complicated geometries have not been fully addressed. In this study, we investigate ODW interaction with a Prandtl–Meyer expansion fan due to confinement upstream of the ODW. Numerical simulations are conducted using the reactive Euler equations with a two-step induction–reaction kinetic model. Two ODWs without an expansion fan are first simulated to resolve the basic structures with inflow Mach numbers M0 = 6 and 7. Thereafter, we introduce a Prandtl–Meyer expansion fan generated by the deflected upper confinement, resulting in a new wave configuration. This wave is characterized by a post-turning, triangular recirculation zone coupled with a gaseous wedge connecting the deflection point and ODW surface. A parametric study is performed to analyze effects of the deflection location, deflection angle, and activation energy of the heat release reaction. The results reveal that the wave configuration is due to the evolution of ODW decoupling in an expanded supersonic flow. We further study the surface stability and structural unsteadiness arising for M0 = 6. Upstream-traveling transverse waves are observed for the first time, and effects of different parameters on the surface instability are analyzed via fast Fourier transform. Two destabilizing mechanisms of ODW structures are proposed, one from the post-surface thermal choking and the other from the enhanced surface instability.