Publication

Abstract : The URANS method is employed to investigate the self-excited oscillation and forced oscillation of the shock train by varying the upstream turbulence intensity and applying pressure fluctuations at the upstream and downstream of the model, respectively. The current results demonstrate that while turbulence intensity is extremely low or high, the probability distribution of instantaneous shock train positions tends toward uniformity within the oscillation region. As the upstream turbulence intensity rises, the shock train leading edge shifts closer to the upstream. Meanwhile, the oscillation of the first shock is intensified, while the second shock exhibits the opposite behavior. The oscillation energy of the downstream shocks decreases. Upstream imposed disturbances propagate to the isolator exit, while downstream disturbances remain confined to propagation within the shock train. Peak frequencies are observed in the power spectral density analyses, where their harmonics serve as a critical factor causing the shock train to follow distinct trajectories during each perturbation cycle. Increasing perturbation frequency reduces shock train oscillation amplitudes and weakens the impact of dominant frequency oscillations on other frequency components. Upstream and downstream frequency variations of the isolator exhibit opposing effects on shock train length, though the length variation shows no correlation with perturbation amplitude. As the perturbation amplitude increases, a reduction in the gas acceleration zone behind the leading shock is observed. In comparison to upstream perturbations, downstream ones induce more pronounced impacts on the distance between the first two shocks.