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Aeroacoustic performance of fractal spoilers

Aeroacoustic performance of fractal spoilers
Aeroacoustic performance of fractal spoilers
One of the major environmental problems facing the aviation industry is that of aircraft noise. The work presented in this paper, done as part of the European Union’s Optimisation for Low Environmental Noise Impact Project, looks at reducing spoiler noise while maintaining aerodynamic performance, through means of large-scale fractal porosity. It is hypothesized that the highly turbulent flow generated by fractal grids from the way the multiple-length scales are organized in space, would reduce the impact of the recirculation region and, with it, thelow-frequency noise it generates. In its place, a higher frequency noise is introduced, which is more susceptible to atmospheric attenuation and is less offensive to the human ear. A total of nine laboratory-scaled spoilers were looked at, seven of which had a fractal design, one with a regular grid design, and one solid for reference. The spoilers were inclined at an angle of 30 deg. Force, acoustic, and flow visualization experiments on a flat plate were carried out and it was found that the present fractal spoilers reduce the low-frequency noise by 2.5 dB. Results show that it is possible to improve the acoustic performance by modifying a number of parameters defining the fractal spoiler, some of them very sensitively. From these experiments, two fractal spoilers were chosen for a detailed aeroacoustic study on a three element wing system, where it was found that the fractal spoilers had a reduction of up to 4 dB in the sound pressure level, while maintaining similar aerodynamic performances as conventional solid spoilers on the measured wing system
0001-1452
2695-2710
Nedic, J.
1ffd220b-4d72-40f9-9f85-d4dc9fef0cfe
Ganapathisubramani, B.
5e69099f-2f39-4fdd-8a85-3ac906827052
Vassilicos, J.C.
e3e74602-557c-450b-aa9a-3d28a1721f1a
Borée, J.
b7525383-4284-4985-84c1-7af3caceac26
Brizzi, L.E.
b534305c-9ef4-4b80-9261-1cd976f1c6f3
Spohn, A.
d5d50c38-54a0-400c-b5cd-8fc94173e34f
Nedic, J.
1ffd220b-4d72-40f9-9f85-d4dc9fef0cfe
Ganapathisubramani, B.
5e69099f-2f39-4fdd-8a85-3ac906827052
Vassilicos, J.C.
e3e74602-557c-450b-aa9a-3d28a1721f1a
Borée, J.
b7525383-4284-4985-84c1-7af3caceac26
Brizzi, L.E.
b534305c-9ef4-4b80-9261-1cd976f1c6f3
Spohn, A.
d5d50c38-54a0-400c-b5cd-8fc94173e34f

Nedic, J., Ganapathisubramani, B., Vassilicos, J.C., Borée, J., Brizzi, L.E. and Spohn, A. (2012) Aeroacoustic performance of fractal spoilers. AIAA Journal, 50 (12), 2695-2710. (doi:10.2514/1.j051387).

Record type: Article

Abstract

One of the major environmental problems facing the aviation industry is that of aircraft noise. The work presented in this paper, done as part of the European Union’s Optimisation for Low Environmental Noise Impact Project, looks at reducing spoiler noise while maintaining aerodynamic performance, through means of large-scale fractal porosity. It is hypothesized that the highly turbulent flow generated by fractal grids from the way the multiple-length scales are organized in space, would reduce the impact of the recirculation region and, with it, thelow-frequency noise it generates. In its place, a higher frequency noise is introduced, which is more susceptible to atmospheric attenuation and is less offensive to the human ear. A total of nine laboratory-scaled spoilers were looked at, seven of which had a fractal design, one with a regular grid design, and one solid for reference. The spoilers were inclined at an angle of 30 deg. Force, acoustic, and flow visualization experiments on a flat plate were carried out and it was found that the present fractal spoilers reduce the low-frequency noise by 2.5 dB. Results show that it is possible to improve the acoustic performance by modifying a number of parameters defining the fractal spoiler, some of them very sensitively. From these experiments, two fractal spoilers were chosen for a detailed aeroacoustic study on a three element wing system, where it was found that the fractal spoilers had a reduction of up to 4 dB in the sound pressure level, while maintaining similar aerodynamic performances as conventional solid spoilers on the measured wing system

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More information

Published date: December 2012
Organisations: Aerodynamics & Flight Mechanics Group

Identifiers

Local EPrints ID: 354992
URI: http://eprints.soton.ac.uk/id/eprint/354992
ISSN: 0001-1452
PURE UUID: ea2c8db0-3b0d-4e78-b017-b1d8ab3f18bd
ORCID for B. Ganapathisubramani: ORCID iD orcid.org/0000-0001-9817-0486

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Date deposited: 12 Aug 2013 10:35
Last modified: 15 Mar 2024 03:37

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Contributors

Author: J. Nedic
Author: J.C. Vassilicos
Author: J. Borée
Author: L.E. Brizzi
Author: A. Spohn

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