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Permeable Surface Corrections for Ffowcs Williams and Hawkings IntegralsThe acoustic prediction methodology discussed herein applies an acoustic analogy to calculate the sound generated by sources in an aerodynamic simulation. Sound is propagated from the computed flow field by integrating the Ffowcs Williams and Hawkings equation on a suitable control surface. Previous research suggests that, for some applications, the integration surface must be placed away from the solid surface to incorporate source contributions from within the flow volume. As such, the fluid mechanisms in the input flow field that contribute to the far-field noise are accounted for by their mathematical projection as a distribution of source terms on a permeable surface. The passage of nonacoustic disturbances through such an integration surface can result in significant error in an acoustic calculation. A correction for the error is derived in the frequency domain using a frozen gust assumption. The correction is found to work reasonably well in several test cases where the error is a small fraction of the actual radiated noise. However, satisfactory agreement has not been obtained between noise predictions using the solution from a three-dimensional, detached-eddy simulation of flow over a cylinder.
Document ID
20050182105
Document Type
Preprint (Draft being sent to journal)
Authors
Lockard, David P. (NASA Langley Research Center Hampton, VA, United States)
Casper, Jay H. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 2005
Subject Category
Acoustics
Report/Patent Number
AIAA Paper 2005-2995
Meeting Information
11th AIAA/CEAS Aeroacoustics Conference(Monterey, CA)
Funding Number(s)
OTHER: 23-781-10-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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