Back-Pressure Effects on the Hypersonic Inlet-Isolator Pseudoshock Motions

Abstract

A three-dimensional unsteady Reynolds-averaged Navier–Stokes equation solver has been developed to investigate the effects of backpressure on the flowfield unsteadiness, pseudoshock oscillation, and the velocity of the unstart shock wave in the hypersonic inlet isolator when the total temperature is 1800 K. The results showed that, when the ratio of backpressure to the freestream static pressure is 50, the whole flowfield can hold steady; as the ratio increases to 70, the flowfield turns unsteady, and the pseudoshock oscillates with a frequency of 3107 Hz; and when the ratio increases to 90, the inlet unstarts and oscillates with a frequency of about 597 Hz. The maximum amplitude of static pressure fluctuation occurs in the range where the leading-edge shock of the shock trains oscillates. The lower-wall pressure reaches its peak value when the first shock wave of the pseudoshock oscillates to its most upstream position and decreases to its minimum value when the leading-edge shock wave of the pseudoshock oscillates to its most downstream position. Besides the total temperature, the backpressure also affects the propagation speed of unstart shock wave; the greater the backpressure is, the quicker the unstart shock wave moves.