Theoretical considerations on shock reflections and their implications on the evaluation of air intake performance

Many theoretical studies have shown the existence of a hysteresis effect in the solution of oblique shock reflections, In fact, a wide domain of free- stream Mach number and shock angle values exists where regular reflection a nd Mach reflection are both possible solutions: fur the same flow condition s, Part of this domain overlaps the typical operating conditions of superso nic air intakes, and therefore it is of practical interest to obtain a deep er understanding of the theoretical problem. Indeed, although both solution s are theoretically possible, they yield very different flowfields and cons equently large discrepancies in the evaluation of the air intake performanc e. Numerical solutions fur steady configurations have been carried out and compared with the flow evolution obtained for time-dependent cases. The res ults have confirmed numerically the existence of the multiple solution doma in where hysteresis takes place ill time-dependent simulations. The analysi s of the physical and numerical problems encountered has provided indicatio ns for a correct simulation in practical applications.