Interaction of a Normal Shock Wave with Small Pressure Disturbances in a Diffuser

The response of a normal shock wave in a transonic or a supersonic diffuser to small-amplitude pressure disturbnaces introduced downstream of the shock wave is analyzed with the method of small perturbations. Numerical results are given for a two-dimensional circular diffuser. The subsequent shock wave motion is classified into a stable oscillation about the initial steady flow shock position and an unstable case where the shock wave moves upstream of the throat, depending on the frequency of the pressure disturbance, the initial shock position, and the diffuser efficiency of the subsonic region downstream of the shock wave. The stability criterion of the shock wave is shown with example calculations