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Analytic Formulation and Numerical Implementation of an Acoustic Pressure Gradient PredictionTwo new analytical formulations of the acoustic pressure gradient have been developed and implemented in the PSU-WOPWOP rotor noise prediction code. The pressure gradient can be used to solve the boundary condition for scattering problems and it is a key aspect to solve acoustic scattering problems. The first formulation is derived from the gradient of the Ffowcs Williams-Hawkings (FW-H) equation. This formulation has a form involving the observer time differentiation outside the integrals. In the second formulation, the time differentiation is taken inside the integrals analytically. This formulation avoids the numerical time differentiation with respect to the observer time, which is computationally more efficient. The acoustic pressure gradient predicted by these new formulations is validated through comparison with available exact solutions for a stationary and moving monopole sources. The agreement between the predictions and exact solutions is excellent. The formulations are applied to the rotor noise problems for two model rotors. A purely numerical approach is compared with the analytical formulations. The agreement between the analytical formulations and the numerical method is excellent for both stationary and moving observer cases.
Document ID
20090004704
Acquisition Source
Langley Research Center
Document Type
Other
Authors
Lee, Seongkyu (Pennsylvania State Univ. University Park, PA, United States)
Brentner, Kenneth S. (Pennsylvania State Univ. University Park, PA, United States)
Farassat, F. (NASA Langley Research Center Hampton, VA, United States)
Morris, Philip J. (Pennsylvania State Univ. University Park, PA, United States)
Date Acquired
August 24, 2013
Publication Date
April 24, 2008
Subject Category
Numerical Analysis
Report/Patent Number
LF99-6143
Funding Number(s)
WBS: WBS 561581.02.07.07
CONTRACT_GRANT: NNL05AD50P
Distribution Limits
Public
Copyright
Public Use Permitted.

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