OSCILLATION OF CIRCULAR SHOCK-WAVES WITH UPSTREAM NONUNIFORMITY

Until to the authors' previous reports on the oscillation of circular shock waves, investigations have been concerned with situations where the upstream flow is uniform, and oscillation and deformation are indu ced by only downstream conditions. However in the centrifugal compress or, the flow into the diffuser becomes nonuniform due to the impeller wake and the stall in the upstream impeller, which causes deformation and oscillation of the shock wave. Here, the above effects are conside red. The upstream disturbance was generated by cylindrical bars. An im perfectly circular shock wave was induced by the wake, and the oscilla tion state, along with the modes caused by forced oscillation, was inv estigated experimentally. It was found that the basic mode of oscillat ion is predominant and that the oscillation is weaker than in the case of a uniform upstream.