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.

## 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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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: | 15 Dec 2015 13:16 |

Last Modified: | 02 May 2016 08:22 |

DOI: | 10.1121/1.3327814 |