We present a study of three-stream nozzle concepts with potential to reduce takeoff noise of future commercial supersonic aircraft The concepts were evaluated at realistic cycle conditions in a subscale acoustic facility. Computations solving the Reynolds-Averaged Navier-Stokes equations provided insight into the changes in the flow field that can impact noise generation. The investigation encompassed long- and short-cowl nozzles in coaxial and asymmetric arrangements where the third stream was concentrated in the downward azimuthal direction. In coaxial configurations, addition of the third stream makes a modest impact on the noise emission, with a small benefit at high frequencies in the aft arc. This benefit is more evident in short-cowl nozzles. Asymmetric arrangements involved offsetting the tertiary duct and/or application of an internal wedge-shaped deflector. The asymmetry produces significant noise reduction in the direction of the thickened tertiary flow, and is more effective at cycle conditions with high specific thrust. Reduction of the skewness of the far-field pressure fluctuations suggests suppression of Mach wave radiation by the asymmetric tertiary flow.
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