On the reductions of airfoil broadband noise through sinusoidal trailing-edge serrations
On the reductions of airfoil broadband noise through sinusoidal trailing-edge serrations
The present study investigates the efficacy of sinusoidal trailing-edge (TE) serrations as a passive means for the reductions of airfoil broadband noise, theoretically and experimentally. Comprehensive parametric studies were conducted to determine the effect of serration amplitudes and wavelengths on the noise reduction performance of a National Advisory Committee for Aeronautics (NACA) airfoil. Initially, the present paper shows the use of the trailing-edge noise (TNO) model for the accurate predictions of the surface pressure spectrum near the TE and hence the far-field noise using the Wiener-Hopf method. The predicted spectra and the noise reduction levels showed good agreement with the measurements for a wide range of frequencies. The present study reveals that the local maximums of the overall noise reductions occur when the transverse turbulence integral length scale is either 1.2 or 0.2 times the serration wavelength, which corresponds to λ/t=0.833 or 5, where λ and t are the serration wavelength and integral length scale. One of the key findings of the paper is that the serration wavelength at which the highest noise reductions occur when the acoustic emissions vary inversely with the modified Strouhal number Sthm [i.e., wsste(ω)/wbl(ω) 1/Sthm] for narrow (i.e., small wavelengths) and wider serrations (i.e., large wavelengths), where wsste and wbl are the acoustic emissions radiated from the serrated and baseline airfoils. Further, the TE serrations are also observed to reduce leading-edge (LE) noise along with the self-noise, which indicates the efficacy of TE serrations in reducing the total far-field noise.
Airfoil, Broadband noise, Sinusoidal serrations, Trailing edge, Turbulent flows (TF)
Sushil Kumar, Singh
82892dc3-62a6-4f96-a0fd-69230c339d94
Mohit, Garg
026e99bb-d572-495d-8e6b-ec90af489c73
S., Narayanan
fefbd84a-a656-48cc-adcc-57b0b1c171c9
Lorna, Ayton
83340f9c-f7fe-4832-8e52-f534b75c142d
Paruchuri, Chaitanya
5c1def64-6347-4be3-ac2d-b9f6a314b81d
March 2022
Sushil Kumar, Singh
82892dc3-62a6-4f96-a0fd-69230c339d94
Mohit, Garg
026e99bb-d572-495d-8e6b-ec90af489c73
S., Narayanan
fefbd84a-a656-48cc-adcc-57b0b1c171c9
Lorna, Ayton
83340f9c-f7fe-4832-8e52-f534b75c142d
Paruchuri, Chaitanya
5c1def64-6347-4be3-ac2d-b9f6a314b81d
Sushil Kumar, Singh, Mohit, Garg, S., Narayanan, Lorna, Ayton and Paruchuri, Chaitanya
(2022)
On the reductions of airfoil broadband noise through sinusoidal trailing-edge serrations.
Journal of Aerospace Engineering, 35 (2), [04022003].
(doi:10.1061/(ASCE)AS.1943-5525.0001386).
Abstract
The present study investigates the efficacy of sinusoidal trailing-edge (TE) serrations as a passive means for the reductions of airfoil broadband noise, theoretically and experimentally. Comprehensive parametric studies were conducted to determine the effect of serration amplitudes and wavelengths on the noise reduction performance of a National Advisory Committee for Aeronautics (NACA) airfoil. Initially, the present paper shows the use of the trailing-edge noise (TNO) model for the accurate predictions of the surface pressure spectrum near the TE and hence the far-field noise using the Wiener-Hopf method. The predicted spectra and the noise reduction levels showed good agreement with the measurements for a wide range of frequencies. The present study reveals that the local maximums of the overall noise reductions occur when the transverse turbulence integral length scale is either 1.2 or 0.2 times the serration wavelength, which corresponds to λ/t=0.833 or 5, where λ and t are the serration wavelength and integral length scale. One of the key findings of the paper is that the serration wavelength at which the highest noise reductions occur when the acoustic emissions vary inversely with the modified Strouhal number Sthm [i.e., wsste(ω)/wbl(ω) 1/Sthm] for narrow (i.e., small wavelengths) and wider serrations (i.e., large wavelengths), where wsste and wbl are the acoustic emissions radiated from the serrated and baseline airfoils. Further, the TE serrations are also observed to reduce leading-edge (LE) noise along with the self-noise, which indicates the efficacy of TE serrations in reducing the total far-field noise.
Text
On the Reductions of Airfoil Broadband Noise through Sinusoidal Trailing-Edge Serrations
More information
Accepted/In Press date: 22 October 2021
Published date: March 2022
Additional Information:
Funding Information:
The authors gratefully acknowledge that the current work has been supported by Department of science and Technology [DST (SERB (ECR/2016/000640, CRG/2021/000508))] .
Publisher Copyright:
© 2022 American Society of Civil Engineers.
Keywords:
Airfoil, Broadband noise, Sinusoidal serrations, Trailing edge, Turbulent flows (TF)
Identifiers
Local EPrints ID: 456800
URI: http://eprints.soton.ac.uk/id/eprint/456800
ISSN: 0893-1321
PURE UUID: 2b0c41aa-af09-4305-bf23-52160b8a1f1b
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Date deposited: 11 May 2022 16:48
Last modified: 17 Mar 2024 07:15
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Contributors
Author:
Singh Sushil Kumar
Author:
Garg Mohit
Author:
Narayanan S.
Author:
Ayton Lorna
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