Mechanism Study on Local Unstart of Hypersonic Inlet at High Mach Number

A viscous numerical simulation was performed to study the forebody shock reflection at the cowl under the condition of inflow Mach number higher than the design value for different forebody/cowl configurations. With the help of shock reflection theory and numerical simulation, it was found that the shock reflection changed from overall regular reflection wave configuration to overall Mach reflection wave configuration as the cowl angle decreased or the ramp angle increased. Mach reflection in this situation would be harmful; it could result in the shock propagating forward to cause a shock detachment at the cowl lip (the so-called local unstart of inlet in this paper). And the local unstart of inlet essentially resulted from the transition of forebody shock reflection from overall regular reflection to overall Mach reflection at the cowl. It was also found through comparison with inviscid analysis that the viscous effect had to be considered in the local unstart of inlet for practical applications. The obtained results would be useful for the design of hypersonic forebody/cowl configurations.