Hysteretic Behaviors of Separation-Shock Driven by Backpressure in Isolator with Incident Shocks

Experimental and theoretical studies are performed to analyze the hysteresis of the separation shock caused by shock-wave/boundary-layer interaction (SWBLI). Results from the schlieren images exhibit the spatial distribution of the power spectrum of the shock oscillation during the process of passing through the SWBLI region. This distribution indicates that the downstream region of the SWBLI tends to excite the oscillation with a higher power and longer duration. In the periodic motion, the relationship between the velocity of the first separation shock and the varying rate of the downstream pressure shows that the downstream region of the SWBLI has slight retardation on the movement of the separation shock. The analysis based on the dynamic model indicates that the hysteresis of the separation shock in this situation is caused by the nonlinear relationship between the length of the shock system and the flow condition, which forms a dual solution in the pressure distribution within the shock system. When the flap varying rate is below a certain value, the width of the hysteresis loop maintains as the same, which is determined by the distributions of the flow parameters; whereas with a larger varying rate, the dynamic feature of the separation shock should be considered.