# 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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## Description/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 |
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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 |

URI: | http://eprints.soton.ac.uk/id/eprint/147359 |

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