Acoustic radiation characteristics of cutoff modes from ducts

Baddour, B., Joseph, P., Mcalpine, A. and Leung, R. (2022) Acoustic radiation characteristics of cutoff modes from ducts. Journal of Sound and Vibration, 541, [117306]. (doi:10.1016/j.jsv.2022.117306).

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Abstract

The acoustic radiation from a source inside a hard-walled semi-infinite duct or tube, such as for ducted fans and rotors, is investigated. In particular a study of cutoff modes, which have the potential to affect the far-field pressure radiation for sources close to the duct open end, is presented. A large amount of work has been done to mathematically and experimentally investigate propagating cuton acoustic modes. However, there is very little published work on the radiation of cutoff modes. This paper concerns the radiation characteristics of cutoff modes to determine their behaviour, and their likely influence in the far-field directivity for sources close to the duct open end. It is shown that cutoff modes are an essential contributor for the radiation in the rear-arc.

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e-pub ahead of print date: 28 September 2022

Published date: 22 December 2022

Additional Information: Funding Information: Funding for this work was gratefully accepted by the Engineering and Physical Sciences research council, United Kingdom and the Defense Science and Technology Laboratory, United Kingdom . The authors would like to express gratitude to Gwenael Gabard for supplying the code to calculate the directivity patterns for the unflanged duct model.

Keywords: Acoustic, Cutoff, Duct, Modal, Radiation