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CFD and transonic helicopter soundA computational method which predicts far-field impulsive noise from a transonic motor blade is demonstrated. This method couples near-field results from a full-potential finite-difference method with a new Kirchhoff integral formulation to extend the finite-difference results into the acoustic far-field. This Kirchhoff formula is written in a blade-fixed coordinate system. It requires initial data from the potential code on a plane at the sonic radius. A recent hovering rotor experiment is described where accurate pressure measurements were recorded on the sonic cylinder and at 2 and 3 radii. The potential code prediction of sonic cylinder pressures is excellent. Acoustic far-field pressure predictions show good agreement with hover experimental data over the range of speeds from 0.85 to 0.92 tip Mach number, the latter of which have delocalized transonic flow. These results are some of the first successful predictions for peak pressure amplitudes using a computational code.
Document ID
19900055378
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Purcell, Timothy W.
(NASA Ames Research Center; U.S. Army, Aeroflightdynamics Directorate, Moffett Field CA, United States)
Date Acquired
August 14, 2013
Publication Date
September 1, 1988
Subject Category
Acoustics
Accession Number
90A42433
Distribution Limits
Public
Copyright
Other

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