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. The Journal of the Acoustical Society of America, 127, (4), 2159-2168. (doi:10.1121/1.3327814).


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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
ISSNs: 0001-4966 (print)
Keywords: acoustic noise, acoustic wave propagation, aeroacoustics, subsonic flow
Subjects: Q Science > QC Physics
T Technology > T Technology (General)
Divisions: University Structure - Pre August 2011 > Institute of Sound and Vibration Research > Fluid Dynamics and Acoustics
ePrint ID: 147359
Date Deposited: 23 Apr 2010 15:01
Last Modified: 27 Mar 2014 19:07

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