Rotor Blade-Vortex Interaction Impulsive Noise Source Localization.

Abstract

An acoustic source localization scheme applicable to noncompact moving sources is developed and applied to the blade-vortex interaction (BVI) noise data of a 40 % scale BO-105 model rotor. A generalized rotor wake code is employed to predict possible BVI locations on the rotor disk and is found useful in interpreting the acoustic localization results. The highly varying directivity patterns of different BVI impulses generated at the same test condition is explained by both the localization results and predicted tip vortex trajectories. The effects of rotor tip-path-plane angle and advance ratio on the BVI source positions is studied. Decreasing tip-path-plane angle moves the general interaction region upwind on the rotor disk, significantly changing the interaction geometry. The region of strongest BVI sources lies between 60- and 70-deg azimuth and 80 and 90 % radius.