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

Sinayoko, S and Joseph, P and McAlpine, A (2010) Multimode radiation from an unflanged, semi-infinite circular duct with uniform flow. J Acoust Soc Am, 127. pp. 2159-2168.

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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.

Item Type: Article
Uncontrolled Keywords: Acoustics Computer Simulation Engineering Equipment Design Models, Theoretical Motion Noise Numerical Analysis, Computer-Assisted Pressure
Subjects: UNSPECIFIED
Divisions: Div A > Fluid Mechanics
Depositing User: Cron Job
Date Deposited: 07 Mar 2014 11:43
Last Modified: 28 Jul 2014 01:09
DOI: 10.1121/1.3327814

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