Numerical investigation of shock train characteristics in an annular isolator under incident shock waves and rotating backpropagation pressure wave

To study the characteristics of shock train in the isolator of a rotating detonation ramjet engine, three-dimensional unsteady RANS simulations were conducted on annular isolators under the influence of uniform incoming flow and incident shock waves, respectively, with the effect of rotating detonation waves simulated by a rotating unsteady pressure exhibiting high-frequency and non-uniform features. Compared to uniform incoming flow, the shock train exhibits significant asymmetry under the influence of incident shock waves. The wall toward which the shock train is biased is directly affected by the wave system within the shock train. The mechanism analysis indicates that the shock train is biased toward the wall with higher pressure at the shock train's leading edge. The shock train's bias varies circumferentially, causing the backpropagation pressure wave propagating spirally upstream to exhibit circumferential fluctuations. During the backpropagation pressure wave propagating upstream, the propagation speed gradually decreases, and the shape evolves from shock wave to shock train. The shock train's leading edge oscillates periodically under the backpropagation pressure wave. Under uniform incoming flow, the oscillation range on the inner and outer walls is basically consistent. Compared to uniform incoming flow, under the influence of incident shock wave, the oscillation amplitude of the shock train's leading edge is smaller, with the most upstream position on the inner wall being further upstream, while on the outer wall, it is slightly further downstream. The dominant frequency of the wall pressure oscillation is consistent with the rotating frequency of the rotating backpressure.