Unstarting/starting characteristics of supersonic inlet investigated by wind tunnel test and Reynolds-stress-compensated scale-adaptive simulation

To comprehend the unstarting/starting characteristics influenced by the freestream Mach number, a rectangular supersonic inlet is investigated in the continuously variable Mach number wind tunnel. Three typical states have been identified: the pseudo unstart state, the pseudo start state, and the fully started state. To further analyze the details of unsteady flow, the inlet under these typical states (corresponding to three freestream Mach numbers, 2.27, 2.31, and 2.49) is numerically investigated by means of the Reynolds-stress-compensated scale-adaptive simulation technique. The flow structure and static pressure from the experimental and numerical results are in good agreement, which indicates the applicability and effectiveness of the current numerical strategy. The relationship between the performance and the shock and turbulent boundary layer interaction (STBLI) is analyzed. In addition, the visualizations of shock evolution and instantaneous vortex structures are employed to observe the flow details. In the pseudo unstart state, the bow shock is discovered at the lip. Due to the STBLI, large-scale vortex structures emerge and continuously evolve, with significant flow separation. In pseudo start and fully started states, the oblique shock appears at the lip, and the flow separation is significantly reduced. In addition, the flow within the isolator becomes similar to the channel flow, which is demonstrated by the transient velocity fluctuations. Analyses of Reynolds stress and turbulence anisotropy have clarified the distinction between the turbulence properties under different states.