Alteration of Jet Noise by Jet Plume Deflection

The impact of deflecting the jet plume on jet noise is investigated. When a convergent single-stream nozzle is beveled, the plume deflects towards the short lip of the beveled nozzle. Thus, there is seemingly the same deflection introduced by both the canting and the beveling of a round nozzle. The observed noise reduction for the different beveled geometries is due to the modification of the noise radiation mechanisms and not due to the deflection of the jet plume that can be achieved with canting or swiveling of the round nozzle. The performances of the beveled nozzles are assessed against the reference round nozzle. With a scale factor of eight, the measured model frequency range is adequate to resolve the engine scale frequency range of 50 Hz to 10 kHz, which is used in the computation of the PNLT. The effect of the reduction in flow area is also taken into account, by increasing the scale factor such that the mass flow rates for the round and beveled nozzles are identical.