Multimode radiation from an unflanged, semi-infinite circular duct with uniform flow
Multimode radiation from an unflanged, semi-infinite circular duct with uniform flow
Multimode sound radiation from an unflanged, semi-infinite, rigid-walled circular duct with uniform subsonic mean flow everywhere is investigated theoretically. The multimode directivity depends on the amplitude and directivity function of each individual cut-on mode. The amplitude of each mode is expressed as a function of cut-on ratio for a uniform distribution of incoherent monopoles, a uniform distribution of incoherent axial dipoles, and for equal power per mode. The directivity function of each mode is obtained by applying a Lorentz transformation to the zero-flow directivity function, which is given by a Wiener–Hopf solution. This exact numerical result is compared to an analytic solution, valid in the high-frequency limit, for multimode directivity with uniform flow. The high-frequency asymptotic solution is derived assuming total transmission of power at the open end of the duct, and gives the multimode directivity function with flow in the forward arc for a general family of mode amplitude distribution functions. At high frequencies the agreement between the exact and asymptotic solutions is shown to be excellent.
acoustic noise, acoustic wave propagation, aeroacoustics, subsonic flow
2159-2168
Sinayoko, Samuel
0e4346ca-1a26-481d-8241-f83730f6b0e4
Joseph, Philip
9c30491e-8464-4c9a-8723-2abc62bdf75d
McAlpine, Alan
aaf9e771-153d-4100-9e84-de4b14466ed7
April 2010
Sinayoko, Samuel
0e4346ca-1a26-481d-8241-f83730f6b0e4
Joseph, Philip
9c30491e-8464-4c9a-8723-2abc62bdf75d
McAlpine, Alan
aaf9e771-153d-4100-9e84-de4b14466ed7
Sinayoko, Samuel, Joseph, Philip and McAlpine, Alan
(2010)
Multimode radiation from an unflanged, semi-infinite circular duct with uniform flow.
Journal of the Acoustical Society of America, 127 (4), .
(doi:10.1121/1.3327814).
Abstract
Multimode sound radiation from an unflanged, semi-infinite, rigid-walled circular duct with uniform subsonic mean flow everywhere is investigated theoretically. The multimode directivity depends on the amplitude and directivity function of each individual cut-on mode. The amplitude of each mode is expressed as a function of cut-on ratio for a uniform distribution of incoherent monopoles, a uniform distribution of incoherent axial dipoles, and for equal power per mode. The directivity function of each mode is obtained by applying a Lorentz transformation to the zero-flow directivity function, which is given by a Wiener–Hopf solution. This exact numerical result is compared to an analytic solution, valid in the high-frequency limit, for multimode directivity with uniform flow. The high-frequency asymptotic solution is derived assuming total transmission of power at the open end of the duct, and gives the multimode directivity function with flow in the forward arc for a general family of mode amplitude distribution functions. At high frequencies the agreement between the exact and asymptotic solutions is shown to be excellent.
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e-pub ahead of print date: 5 April 2010
Published date: April 2010
Keywords:
acoustic noise, acoustic wave propagation, aeroacoustics, subsonic flow
Organisations:
Fluid Dynamics & Acoustics Group
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Local EPrints ID: 147359
URI: http://eprints.soton.ac.uk/id/eprint/147359
ISSN: 0001-4966
PURE UUID: 680e2d5a-398c-4c28-887a-c01ca4793f9d
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Date deposited: 23 Apr 2010 15:01
Last modified: 14 Mar 2024 02:42
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Author:
Samuel Sinayoko
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