Impacts of panel vibration and fluctuating backpressure on shock train behavior in scramjet isolators

Considering the weight limitations of hypersonic vehicles and the requirements of thermal protection structure design, the adoption of thin-walled structures in scramjet isolators is an inevitable choice. However, the pressure pulsations generated in the combustion chamber, coupled with panel vibrations induced by thin-walled structures, generate unsteady effects on the shock-wave/boundary-layer interaction in an isolator. This study focuses on this problem by utilizing the unsteady Reynolds-averaged Navier–Stokes equations and dynamic grid technology to investigate the combined effects of wall panel vibrations and fluctuating backpressure on shock train structures, wall aerodynamic loads, and aerodynamic performance. The effects of vibration location and frequency of the panel structure are systematically investigated. The results indicate that the oscillation frequency of the flow field is a combination of the backpressure pulsation frequency and the wall panel vibration frequency, and the shock train exhibits a periodic alternation between large-amplitude and small-amplitude oscillations. The panel vibration will cause greater non-uniformity of the outlet flow, increase the wall pressure oscillations load and amplitude increase in the shock train, reducing the ability of the isolator to resist backpressure. The influence of panel vibration strongly depends on its position and frequency: upstream wall vibrations exert the most significant effect on shock train amplitude and pressure fluctuations, while low-frequency vibrations (f < 400 Hz) intensify oscillations more markedly than high-frequency vibrations (f ≥ 400 Hz).