Fundamental characteristics of Blade Wake Interaction (BWI) noise are determined, 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 tip vortices. The data are from the rotor aeroacoustic test program called HART that was jointly conducted by European and American government agencies in the German-Dutch Wind Tunnel, DNW. The test data include simultaneous measurements of instantaneous blade pressures and acoustic time histories. 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 blade pressure contours over the rotor disk are presented. Causality relations between the blade pressures and acoustic data are developed for the prediction of BWI noise. The predictions use blade response coherence functions obtained using cross-spectral methods. Comparison between predicted and measured noise shows good agreement over the large range of rotor flight tilt angles of the test. This success demonstrates that the causality of the BWI noise problem is established and the prediction code can form a basis of a comprehensive rotor broadband noise capability.
Blade wake interaction noise for a main rotor
Blatt-Nachlauf-Wechselwirkungsgeräusch bei einem Hauptrotor
Journal of the American Helicopter Society ; 49 , 1 ; 11-27
2004
17 Seiten, 31 Bilder, 33 Quellen
Aufsatz (Zeitschrift)
Englisch
Blade Wake Interaction Noise for a Main Rotor
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