Correlation Between Subsonic Jet Screech and Eddy Structure

The explanation of the influence of the exit divergent angle of nozzle on the subsonic jet noise is very important. It was found that the jet issuing from the divergent angle nozzle of 10°-30° produced a powerful screech contained the discrete frequencies. To clarify the mechanism in the generation of powerful screech, a flow visualization was carried out by means of the instantaneous schlieren photograph method. It is proved that there is a series of dynamic eddies moving with jet flow near by the exit of nozzle, and it is due to the self-excited vibration occuring in the dynamic eddies region that the powerful screech is produced.