Slanted septum and multiple folded cavity liners for broadband sound absorption
Slanted septum and multiple folded cavity liners for broadband sound absorption
The design of acoustic liners with complex cavities for a wide frequency range of attenuation using numerical method is investigated in this paper. Three novel liner concepts are presented, demonstrating predicted improvements in broadband sound absorption when compared with that for conventional designs. The liners include a slanted septum core, a slanted septum core with varying percentage open area, and a MultiFOCAL concept. A finite element model of a normal incidence impedance tube is developed using COMSOL Multiphysics modeling software to predict the acoustic properties (resistance and reactance) of liners at medium and high sound pressure levels, and to study the impact of variations in the liner design parameters. The impedance tube finite element model incorporates non-linear semi-empirical impedance equations, validated by comparing numerical results with measurements performed on a single-degree-of-freedom liner, with a perforated face sheet, at high sound pressure level. The design variables of the novel liner concepts are optimized using a hybrid automated optimisation procedure. The low-frequency optimum slanted septum core concept with an open area of 4.5% for the face sheet and 18% for the short slanted septum is predicted to have an absorption level of at least 14 dB in the frequency range of 400– 1000 Hz for normally incident pure tone excitations at 150 dB. The slanted septum core concept with varying percentage open area, with broadband optimum design variables, is predicted to have good broadband sound absorption levels of at least 10 dB in the frequency range of 570–3800 Hz. Finally, the MultiFOCAL liner concept with optimised percentage open areas is predicted to have an excellent broadband sound absorption levels of at least 14 dB, for pure tone excitations at 150 dB, in the frequency range of 900–5300 Hz. This work will be followed by optimisation of the face sheet geometries of these novel liner designs in order to maximise lined duct attenuation for aircraft engine applications.
Novel liners, broadband sound absorption, high sound pressure level, multiple folded cavities, optimization, perforated slanted septum
633-661
Palani, Suresh
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Murray, Paul
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McAlpine, Alan
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Sasaki, Daisuke
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Richter, Christophe
93e6acfc-c7ed-4515-89be-7ecd42e18519
September 2021
Palani, Suresh
0f4665c3-885a-4fb6-a957-bbc947e340b8
Murray, Paul
f0b1a0c8-6913-4238-9544-263723a80901
McAlpine, Alan
aaf9e771-153d-4100-9e84-de4b14466ed7
Sasaki, Daisuke
1d400b29-02c8-42f9-8bbc-47cdc12ec5fa
Richter, Christophe
93e6acfc-c7ed-4515-89be-7ecd42e18519
Palani, Suresh, Murray, Paul, McAlpine, Alan, Sasaki, Daisuke and Richter, Christophe
(2021)
Slanted septum and multiple folded cavity liners for broadband sound absorption.
International Journal of Aeroacoustics, 20 (5-7), , [1475472X2110238].
(doi:10.1177/1475472X211023835).
Abstract
The design of acoustic liners with complex cavities for a wide frequency range of attenuation using numerical method is investigated in this paper. Three novel liner concepts are presented, demonstrating predicted improvements in broadband sound absorption when compared with that for conventional designs. The liners include a slanted septum core, a slanted septum core with varying percentage open area, and a MultiFOCAL concept. A finite element model of a normal incidence impedance tube is developed using COMSOL Multiphysics modeling software to predict the acoustic properties (resistance and reactance) of liners at medium and high sound pressure levels, and to study the impact of variations in the liner design parameters. The impedance tube finite element model incorporates non-linear semi-empirical impedance equations, validated by comparing numerical results with measurements performed on a single-degree-of-freedom liner, with a perforated face sheet, at high sound pressure level. The design variables of the novel liner concepts are optimized using a hybrid automated optimisation procedure. The low-frequency optimum slanted septum core concept with an open area of 4.5% for the face sheet and 18% for the short slanted septum is predicted to have an absorption level of at least 14 dB in the frequency range of 400– 1000 Hz for normally incident pure tone excitations at 150 dB. The slanted septum core concept with varying percentage open area, with broadband optimum design variables, is predicted to have good broadband sound absorption levels of at least 10 dB in the frequency range of 570–3800 Hz. Finally, the MultiFOCAL liner concept with optimised percentage open areas is predicted to have an excellent broadband sound absorption levels of at least 14 dB, for pure tone excitations at 150 dB, in the frequency range of 900–5300 Hz. This work will be followed by optimisation of the face sheet geometries of these novel liner designs in order to maximise lined duct attenuation for aircraft engine applications.
Text
Novel Liners IJA Paper Revised Final
- Accepted Manuscript
More information
Accepted/In Press date: 2021
e-pub ahead of print date: 9 June 2021
Published date: September 2021
Additional Information:
Funding Information:
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant No. 769350.
Publisher Copyright:
© The Author(s) 2021.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
Keywords:
Novel liners, broadband sound absorption, high sound pressure level, multiple folded cavities, optimization, perforated slanted septum
Identifiers
Local EPrints ID: 449854
URI: http://eprints.soton.ac.uk/id/eprint/449854
ISSN: 1475-472X
PURE UUID: 596abf63-a648-466b-944c-20c76adc2c42
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Date deposited: 22 Jun 2021 16:31
Last modified: 17 Mar 2024 02:47
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Author:
Suresh Palani
Author:
Daisuke Sasaki
Author:
Christophe Richter
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