Effects of Dynamic Backpressure on Pseudoshock Oscillations in Scramjet Inlet-Isolator

Abstract

To estimate the effects of combustion-induced backpressure on the pseudoshock oscillation within a scramjet inlet isolator, a computational-fluid-dynamics code was used to study the motions of pseudoshock under different sinusoidal dynamic backpressures. The relations of the pseudoshock oscillation with the pressure histories, standard deviation, and spectral density distributions were explored. Second, the impact of frequency and amplitude of dynamic backpressure on the pseudoshock oscillation was investigated. The results show that the leading edge of the oscillating pseudoshock is not at the place where maximum values of standard deviation and spectral density occur because sinusoidal dynamic backpressure is applied at the exit of the isolator. Moreover, the frequencies of dynamic backpressure have minor influence on the maximum upstream position of the pseudoshock leading edge with the increase of frequency. In comparison, the amplitudes of the dynamic backpressures have great impact on the maximum upstream and downstream locations of the pseudoshock leading edge. It was also revealed that, although the flowfields as well as the locations of pseudoshock leading edge are quite different, the standard deviation and spectral density distributions are nearly the same for the case of sinusoidal backpressure applied.