Numerical investigation of inlet buzz flow

The present research aims at developing a time-accurate, high-resolution total variation diminishing scheme and a data-processing procedure that can analyze the inlet buzz flow problem. Special care has been exercised on the numerical buzz flow initiation procedure to minimize the generation of spurious numerical waves. A 10-ft ramjet engine was adopted as the simulation model. The simulated results show that the buzz cycle is attributed both to the local flow instability around the entrance and to the acoustic resonance modes appearing inside the plenum chamber. A revised upstream feedback mechanism is proposed in the present work. It was found that the feedback loop for the subcritical operation is established locally around the inlet region, in which the reflected acoustic waves were sent upstream as a result of the impingement of the shock-induced separation vorticities on the centerbody surface and/or the cowl lip. For the supercritical operation, however, the formation of the feedback mechanism is ascribed to the fundamental acoustic resonance node generated in the plenum chamber.