Blade Wake Interaction Noise for a BO-105 Model Main Rotor

Abstract

Fundamental characteristics of Blade Wake Interaction (BWI) noise are determinated, and a prediction method is developed, using acoustic and blade pressure data from a 4-bladed BO-105 model helicopter main rotor. BWI is a broadband noise source caused by the blade interactions with turbulence in the rotor wake, particularly about the tip vortices. The data are from the rotor aeroacoustic test program called HART which was jointly conducted by European and American government agencies in the German-Dutch Wind Tunnel, DNW. The test datainclude simultaneous measurements of instantaneous blade pressures and acoustic time histories as well as averaged data. The statistical character of the BWI is determined from the instantaneous surface pressures. A BWI noise metric is developed and BWI noise directivity contours (similar to those typically presented for BVI noise) are presented and shown to be a function of rotor tip-path-plane angle. Similarly, BWI.