Effects of dynamic backpressure on shock train motions in straight isolator

Abstract A numerical study of an oscillating shock train under different types of sinusoidal backpressure in a straight isolator is conducted. In comparison, the shock train location and structure under steady backpressure are explored at first. The results reveal that the shock train moves upstream in a nonlinear way with the increasing backpressure and it keeps nearly the same structure in the process of moving upstream under a certain range of backpressure. Secondly, the typical characteristic of shock train motions under dynamic backpressure is investigated from many aspects. When subjected to sinusoidal backpressure, the shock train undergoes a consistent and repeatable periodic motion, which is similar to the simple harmonic motion. Moreover, the impacts of frequency, amplitude and the average of dynamic backpressure on shock train motions are discussed systematically in this paper. It is found that the average backpressure has a great influence on the location of shock train oscillating region, which moves upstream as the average backpressure is increased. The amplitude of dynamic backpressure has a noticeable effect on the size of shock train oscillating region, which is positively correlated with the amplitude. The frequency affects both the location and size of shock train oscillating region. As the frequency increases, the oscillating region becomes smaller and closer to the exit of the isolator.

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