A comparative analysis of XV-15 tiltrotor hover test data and WOPWOP predictions incorporating the fountain effectAcoustic measurements from a hovering full-scale XV-15 tiltrotor with the advanced technology blades are presented which show the directionality of fountain effect noise. Predicted activity directivity results are also presented which show agreement with the measured data. The aeroacoustic code, WOPWOP, was used in conjunction with a mathematical model which simulated the fountain/recirculation aerodynamic effect on the rotors' blade surface pressures. The predictions were used to identify the spike character in the measured data as fountain effect associated noise. The directivity of the fountain effect noise was observed to be dominant at the rear of the aircraft with increased intensities 45 degrees below the rotor disk planes.
Document ID
19930045417
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Rutledge, Charles K. (Lockheed Engineering and Sciences Co. Hampton, VA, United States)
Coffen, Charles D. (NASA Langley Research Center Hampton, VA, United States)
George, Albert R. (Cornell Univ. Ithaca, NY, United States)
Date Acquired
August 16, 2013
Publication Date
January 1, 1991
Publication Information
Publication: In: AHS and Royal Aeronautical Society, Technical Specialists' Meeting on Rotorcraft Acoustics(Fluid Dynamics, Philadelphia, PA, Oct. 15-17, 1991, Proceedings (A93-29401 10-71)