Prediction of blade-vortex interaction noise using measured blade pressuresIn the study reported here, blade-vortex interaction noise was predicted using a simplified model of blade pressures measured on a one-seventh scale model AH-1/OLS main rotor. The methods used for the acoustic prediction are based on the acoustic analogy and have been developed by Nakamura (1981) and by Brentner, Nystrom, and Farassat (referred to as the WOPWOP method). The waveforms predicted by the two methods are in good agreement with each other and with the measurements in terms of the number of pulses, the pulse widths, and the separation times between the pulses. The peak amplitude of the dominant pulse may, however, be underpredicted by up to 40 percent, depending on flight conditions. Ways of improving the accuracy of the prediction methods are suggested.
Document ID
19880029355
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Joshi, Mahendra C. (Textron Bell Helicopter Fort Worth, TX, United States)
Liu, Sandy R. (Bell Helicopter Textron, Inc. Fort Worth, TX, United States)
Boxwell, Donald A. (U.S. Army, Aeroflightdynamics Directorate, Moffett Field CA, United States)