다양한 출구조건이 적용된 초음속 흡입구 공력불안정성 수치적 연구

Abstract

The present study numerically investigates the flow instability around supersonic inlet, called inlet buzz. Though the flow conditions change linearly, behavior of inlet buzz alters hysteretically. In order to simulate the inlet buzz hysteretic character, computations are conducted with varying mass flow rate. The mass flow rate condition is controlled by an exit throttling plug which moves back and forth to change an exit area. In this paper, a set of simulations with mass flow rate control are presented. This simulations focus on hysteretic buzz characteristics of supersonic inlet according to mass flow rate and the historic path of the mass flow rate change. Firstly, an inlet buzz case with decreasing mass flow rate is simulated. In this process, the inlet buzz characteristic changes from the first mode of a low frequency regime to the second mode of a high frequency regime. In the next, the effect of the increasing mass flow rate on the inlet buzz is examined. This case shows another kind of the buzz transition that the buzz frequency becomes higher in the third mode. The hysteretic inlet buzz has many similarities to the fundamentals of a pipe-type musical instrument such as self-excited feed-back mechanism and overblowing. Considering the similarities, the hysteretic characteristics of an inlet buzz is discussed in the instrumental acoustic point of view.