Noise was measured from a 457 mm diameter rotor ingesting the wake of a 50.4 mm diameter cylinder located 20 cylinder diameters upstream. Four microphones were positioned on the port side of the rotor and a 251-channel microphone array was positioned on the starboard side. The effect of rotor yaw, advance ratio, and cylinder wake strike position were studied independently. These data were compared to previous studies considering the ingestion of a wall-bounded shear flow. With increasing thrust, the wall bounded flow produced narrower haystacks at the blade passage frequency as well as more harmonics. The source directivity was found to be asymmetric about the rotor geometry and was sensitive to the rotor yaw, advance ratio, and wake strike location. Changes with rotor yaw and wake strike location were explained with a simple line source model, but changes with advance ratio were believed to be a function of the distortion of approach turbulence at high thrust Acoustic maps of the rotor source generated by analysis of multiple sub-arrays of the 251-channel array showed the identified source location moving about the rotor disk as a function of receiver angle. This was shown to be a result of the source directivity as a function of the wake strike location.
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