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Spinning mode acoustic radiation from the flight inletA mathematical model was developed for spinning mode acoustic radiation from a thick wall duct without flow. This model is based on a series of experiments (with and without flow). A nearly pure azimuthal spinning mode was isolated and then reflection coefficients and far field pressure (amplitude and phase) were measured. In our model the governing boundary value problem for the Helmholtz equation is first converted into an integral equation for the unknown acoustic pressure over a disk, S1, near the mouth of the duct and over the exterior surface, S2, of the duct. Assuming a pure azimuthal mode excitation, the azimuthal dependence is integrated out which yields an integral equation over the generator C1 of S1 and the generator C2 of S2. The sound pressure on C1 was approximated by a truncated modal expansion of the interior acoustic pressure. Piecewise linear spline approximation on C2 was used.
Document ID
19840007828
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Moss, W. F.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 4, 2013
Publication Date
November 1, 1983
Subject Category
Acoustics
Report/Patent Number
REPT-83-63
NAS 1.26:172273
NASA-CR-172273
Accession Number
84N15896
Funding Number(s)
CONTRACT_GRANT: NAS1-17130
CONTRACT_GRANT: NAS1-16394
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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