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Multimode radiation from an unflanged, semi-infinite circular duct with uniform flow

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), pp. 2159-2168. (doi:10.1121/1.3327814).

Record type: Article


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


Local EPrints ID: 147359
ISSN: 0001-4966
PURE UUID: 680e2d5a-398c-4c28-887a-c01ca4793f9d
ORCID for Alan McAlpine: ORCID iD

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Date deposited: 23 Apr 2010 15:01
Last modified: 18 Jul 2017 23:03

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