Passive control of supersonic rectangular jets via nozzle trailing-edge modifications

A research program was carried out to explore the effects of nozzle trailin g-edge modifications on the flow structure, jet mixing will! the ambient ai r, and jet noise of a rectangular supersonic jet. Nozzles with one modified trailing edge were used with the intention of enhancing mixing and reducin g noise. The modifications were simple cutouts in the plane of the nozzle w all and acted to induce large-scale streamwise vortices, A rectangular jet, with a design Mach number of 2 and with various trailing edges, was examin ed using optical diagnostics and noise measurements in flow regimes ranging from moderately overexpanded M-j = 1.5 to moderately underexpanded M-j = 2 .5, The results indicated that in nonideally expanded how regimes, one coul d generate pairs of streamwise vortices of various strength and sign and th at the mixing could be significantly enhanced. The results also indicated t hat the modifications could eliminate or at least substantially reduce scre ech noise and could significantly decrease the overall far-field sound pres sure level in the nonideally expanded flow regimes. In the ideally expanded flow regime, the trailing-edge modifications did not seem to induce stream wise vortices and, thus, did not have a substantial effect on the jet mixin g or noise.