On the noise reduction mechanisms of over-tip liners
On the noise reduction mechanisms of over-tip liners
The application of acoustic liners near/directly over a sound source has gained significant interest for the excess noise reduction achieved with Over-the-Rotor (OTR) liners compared to the conventional liner installations at the intake of an aero-engine. However, the mechanism of noise reduction achieved in the OTR liners is not clearly understood. This paper aims to explain this mechanism by considering a static monopole source placed over a finite liner insert with a zero background mean flow. This has been investigated numerically using COMSOL Multiphysics in a half-space domain and compared with reference analytical solutions for infinite lined walls. One of the key findings of the paper is the underlying physics of the source modification mechanism, which has been found to be the interference between the primary noise source and a secondary noise source forming on the liner surface. It is identified through an optimal impedance study that this back-reaction mechanism is dominant when the source is located for a normalised tip gap, e / λ < 0.25 , where e is the distance between the source and the liner surface and λ is the acoustic wavelength. Within this region, there exists an optimum normalised liner length, L / e providing a maximum insertion loss.
29-43
Subramanyam, Ramesh Raja
7ffe1b2a-a3ac-4433-9090-76babf8dafc4
Palani, Suresh
62cb4236-3b73-412f-9bee-8064a6e494c7
Chaitanya, Paruchuri
5c1def64-6347-4be3-ac2d-b9f6a314b81d
Palleja-Cabre, Sergi
b841a96c-05d1-4f08-a197-8693cb3a3f90
Subramanyam, Ramesh Raja
7ffe1b2a-a3ac-4433-9090-76babf8dafc4
Palani, Suresh
62cb4236-3b73-412f-9bee-8064a6e494c7
Chaitanya, Paruchuri
5c1def64-6347-4be3-ac2d-b9f6a314b81d
Palleja-Cabre, Sergi
b841a96c-05d1-4f08-a197-8693cb3a3f90
Subramanyam, Ramesh Raja, Palani, Suresh, Chaitanya, Paruchuri and Palleja-Cabre, Sergi
(2024)
On the noise reduction mechanisms of over-tip liners.
Journal of the Acoustical Society of America, 155 (1), .
(doi:10.1121/10.0023957).
Abstract
The application of acoustic liners near/directly over a sound source has gained significant interest for the excess noise reduction achieved with Over-the-Rotor (OTR) liners compared to the conventional liner installations at the intake of an aero-engine. However, the mechanism of noise reduction achieved in the OTR liners is not clearly understood. This paper aims to explain this mechanism by considering a static monopole source placed over a finite liner insert with a zero background mean flow. This has been investigated numerically using COMSOL Multiphysics in a half-space domain and compared with reference analytical solutions for infinite lined walls. One of the key findings of the paper is the underlying physics of the source modification mechanism, which has been found to be the interference between the primary noise source and a secondary noise source forming on the liner surface. It is identified through an optimal impedance study that this back-reaction mechanism is dominant when the source is located for a normalised tip gap, e / λ < 0.25 , where e is the distance between the source and the liner surface and λ is the acoustic wavelength. Within this region, there exists an optimum normalised liner length, L / e providing a maximum insertion loss.
Text
Manuscript_Submission_OTR_JASA
- Accepted Manuscript
More information
Accepted/In Press date: 21 November 2023
e-pub ahead of print date: 3 January 2024
Additional Information:
Funding Information:
This work has received funding from the Royal Academy of Engineering (RF). The authors also wish to acknowledge the continuing support provided by Rolls–Royce plc through the University Technology Centre in Propulsion Systems Noise at the Institute of Sound and Vibration Research.
© 2024 Acoustical Society of America.
© 2024 Acoustical Society of America.
Identifiers
Local EPrints ID: 486334
URI: http://eprints.soton.ac.uk/id/eprint/486334
ISSN: 0001-4966
PURE UUID: 2f5a95d8-5cb6-4e13-abb0-df3ae4bffe92
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Date deposited: 18 Jan 2024 18:26
Last modified: 01 May 2024 01:54
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Author:
Ramesh Raja Subramanyam
Author:
Suresh Palani
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