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A numerical study on multimode sound propagation in lined ducts and radiation to the far field

A numerical study on multimode sound propagation in lined ducts and radiation to the far field
A numerical study on multimode sound propagation in lined ducts and radiation to the far field
In previous articles, the authors developed a hybrid scheme for analysing bypass duct noise, in which a numerical analysis using finite element method for in-duct propagation and an analytic radiation code with fully represented effects of bypass shear layer are coupled. Such procedure permits detailed study on the interaction between duct configurations, such as geometry and acoustic liner impedances, and modal propagation and attenuation, and also the effects on the radiation pattern, within practical timescale and at modest computational cost. The scheme has been applied to realistic aero-engine bypass ducts and has been integrated with an optimisation programme. The numerical results obtained so far have revealed that for ducts with acoustic liners highly attenuated modes are not necessarily those with high mode angles, which is contrary to general anticipation. The aim of the study in the current paper is to understand the physics behind this phenomenon and its effect on the radiation to the far field. Detailed investigation on modal attenuation is performed by using the hybrid scheme. The effect of modal power distribution at the duct exit on the directivity pattern of the radiated noise to the far field is also discussed.
Sugimoto, R.
cb8c880d-0be0-4efe-9990-c79faa8804f0
Astley, R.J.
cb7fed9f-a96a-4b58-8939-6db1010f9893
McAleer, C.R.
6dd2a598-f09a-48e7-ac2f-65da43d3a3f5
Achunche, I.
c4fb7ed1-013b-44df-8582-b65813e21e5f
Sugimoto, R.
cb8c880d-0be0-4efe-9990-c79faa8804f0
Astley, R.J.
cb7fed9f-a96a-4b58-8939-6db1010f9893
McAleer, C.R.
6dd2a598-f09a-48e7-ac2f-65da43d3a3f5
Achunche, I.
c4fb7ed1-013b-44df-8582-b65813e21e5f

Sugimoto, R., Astley, R.J., McAleer, C.R. and Achunche, I. (2008) A numerical study on multimode sound propagation in lined ducts and radiation to the far field. Acoustics'08 Paris. 29 Jun - 04 Jul 2008.

Record type: Conference or Workshop Item (Paper)

Abstract

In previous articles, the authors developed a hybrid scheme for analysing bypass duct noise, in which a numerical analysis using finite element method for in-duct propagation and an analytic radiation code with fully represented effects of bypass shear layer are coupled. Such procedure permits detailed study on the interaction between duct configurations, such as geometry and acoustic liner impedances, and modal propagation and attenuation, and also the effects on the radiation pattern, within practical timescale and at modest computational cost. The scheme has been applied to realistic aero-engine bypass ducts and has been integrated with an optimisation programme. The numerical results obtained so far have revealed that for ducts with acoustic liners highly attenuated modes are not necessarily those with high mode angles, which is contrary to general anticipation. The aim of the study in the current paper is to understand the physics behind this phenomenon and its effect on the radiation to the far field. Detailed investigation on modal attenuation is performed by using the hybrid scheme. The effect of modal power distribution at the duct exit on the directivity pattern of the radiated noise to the far field is also discussed.

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More information

Published date: 2008
Additional Information: Abstract no. 2612
Venue - Dates: Acoustics'08 Paris, 2008-06-29 - 2008-07-04

Identifiers

Local EPrints ID: 63666
URI: https://eprints.soton.ac.uk/id/eprint/63666
PURE UUID: f34a6364-f63f-42b1-9cf2-25d344070672

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Date deposited: 23 Oct 2008
Last modified: 13 Mar 2019 20:24

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