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Fuselage boundary-layer refraction of fan tones radiated from an installed turbofan aero-engine

Fuselage boundary-layer refraction of fan tones radiated from an installed turbofan aero-engine
Fuselage boundary-layer refraction of fan tones radiated from an installed turbofan aero-engine
A distributed source model to predict fan tone noise levels of an installed turbofan aero-engine is extended to include the refraction effects caused by the fuselage boundary layer. The model is a simple representation of an installed turbofan, where fan tones are represented in terms of spinning modes radiated from a semi-infinite circular duct, and the aircraft’s fuselage is represented by an infinitely long, rigid cylinder. The distributed source is a disc, formed by integrating infinitesimal volume sources located on the intake duct termination. The cylinder is located adjacent to the disc. There is uniform axial flow, aligned with the axis of the cylinder, everywhere except close to the cylinder where there is a constant thickness boundary layer. The aim is to predict the near- field acoustic pressure, and in particular to predict the pressure on the cylindrical fuselage which is relevant to assess cabin noise. Thus no far-field approximations are included in the modelling. The effect of the boundary layer is quantified by calculating the area-averaged mean square pressure over the cylinder’s surface with and without the boundary layer included in the prediction model. The sound propagation through the boundary layer is calculated by solving the Pridmore-Brown equation. Results from the theoretical method show that the boundary layer has a significant effect on the predicted sound pressure levels on the cylindrical fuselage, owing to sound radiation of fan tones from an installed turbofan aero-engine.
0001-4966
Gaffney, James
7d1a9e19-a1cc-4066-8d98-e9e29c2a0177
Mcalpine, Alan
aaf9e771-153d-4100-9e84-de4b14466ed7
Kingan, Michael
2d2daafa-d6d7-41aa-a9fc-2307259ac9f0
Gaffney, James
7d1a9e19-a1cc-4066-8d98-e9e29c2a0177
Mcalpine, Alan
aaf9e771-153d-4100-9e84-de4b14466ed7
Kingan, Michael
2d2daafa-d6d7-41aa-a9fc-2307259ac9f0

Gaffney, James, Mcalpine, Alan and Kingan, Michael (2017) Fuselage boundary-layer refraction of fan tones radiated from an installed turbofan aero-engine. Journal of the Acoustical Society of America, 141 (3), [1653]. (doi:10.1121/1.4976965).

Record type: Article

Abstract

A distributed source model to predict fan tone noise levels of an installed turbofan aero-engine is extended to include the refraction effects caused by the fuselage boundary layer. The model is a simple representation of an installed turbofan, where fan tones are represented in terms of spinning modes radiated from a semi-infinite circular duct, and the aircraft’s fuselage is represented by an infinitely long, rigid cylinder. The distributed source is a disc, formed by integrating infinitesimal volume sources located on the intake duct termination. The cylinder is located adjacent to the disc. There is uniform axial flow, aligned with the axis of the cylinder, everywhere except close to the cylinder where there is a constant thickness boundary layer. The aim is to predict the near- field acoustic pressure, and in particular to predict the pressure on the cylindrical fuselage which is relevant to assess cabin noise. Thus no far-field approximations are included in the modelling. The effect of the boundary layer is quantified by calculating the area-averaged mean square pressure over the cylinder’s surface with and without the boundary layer included in the prediction model. The sound propagation through the boundary layer is calculated by solving the Pridmore-Brown equation. Results from the theoretical method show that the boundary layer has a significant effect on the predicted sound pressure levels on the cylindrical fuselage, owing to sound radiation of fan tones from an installed turbofan aero-engine.

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JASA_Gaffneyetal_2017_peer-review_accepted_manuscript - Accepted Manuscript
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More information

Accepted/In Press date: 7 February 2017
e-pub ahead of print date: 31 March 2017
Organisations: Acoustics Group, Inst. Sound & Vibration Research, Education Hub

Identifiers

Local EPrints ID: 406646
URI: http://eprints.soton.ac.uk/id/eprint/406646
ISSN: 0001-4966
PURE UUID: 92a78dea-52cf-42c2-9b6a-da867bb12446
ORCID for Alan Mcalpine: ORCID iD orcid.org/0000-0003-4189-2167

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Date deposited: 18 Mar 2017 02:26
Last modified: 17 Dec 2019 06:19

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