A weak scattering model for tone haystacking
A weak scattering model for tone haystacking
The scattering of sound by turbulence in a jet shear layer is considered. Spectral broadening or 'haystacking' is the process whereby the turbulent, time-varying inhomogeneities in the flow scatter tonal sound fields, which decreases
the level of the incident tone, but increases the broadband level around the frequency of the tone. The scattering process is modelled analytically, using high-frequency asymptotic methods and a weak-scattering assumption. Analytical models for the far-field spectral density of the scattered field are derived for two cases: (1) any polar angle including inside the cone of silence; (2) polar angles outside the cone of silence. At polar angles outside the cone of silence, the predictions from the two models are very similar, but using the second model it is considerably simpler to evaluate the far-field spectral density. Simulation results are compared to experimental data, albeit only at a polar angle of 90º. The model correctly predicts the behaviour of the scattered field as a function of jet velocity and tone frequency. Also simulations at other polar angles and a parametric study are presented. These simulations indicate how the 'haystacking' is predicted to vary as a function of the polar angle, and also as a function of the characteristic length, time and convection velocity scales of the turbulence contained in the jet shear layer.
21pp
McAlpine, A.
aaf9e771-153d-4100-9e84-de4b14466ed7
Powles, C.J.
7566be27-f1fe-4ea0-aca3-3aef19cb72de
Tester, B.J.
1bd4a793-131b-4173-93cc-3eca70b2d116
2009
McAlpine, A.
aaf9e771-153d-4100-9e84-de4b14466ed7
Powles, C.J.
7566be27-f1fe-4ea0-aca3-3aef19cb72de
Tester, B.J.
1bd4a793-131b-4173-93cc-3eca70b2d116
McAlpine, A., Powles, C.J. and Tester, B.J.
(2009)
A weak scattering model for tone haystacking.
15th AIAA/CEAS Aeroacoustics Conference (30th AIAA Aeroacoustics Conference), Miami, USA.
11 - 13 May 2009.
.
Record type:
Conference or Workshop Item
(Paper)
Abstract
The scattering of sound by turbulence in a jet shear layer is considered. Spectral broadening or 'haystacking' is the process whereby the turbulent, time-varying inhomogeneities in the flow scatter tonal sound fields, which decreases
the level of the incident tone, but increases the broadband level around the frequency of the tone. The scattering process is modelled analytically, using high-frequency asymptotic methods and a weak-scattering assumption. Analytical models for the far-field spectral density of the scattered field are derived for two cases: (1) any polar angle including inside the cone of silence; (2) polar angles outside the cone of silence. At polar angles outside the cone of silence, the predictions from the two models are very similar, but using the second model it is considerably simpler to evaluate the far-field spectral density. Simulation results are compared to experimental data, albeit only at a polar angle of 90º. The model correctly predicts the behaviour of the scattered field as a function of jet velocity and tone frequency. Also simulations at other polar angles and a parametric study are presented. These simulations indicate how the 'haystacking' is predicted to vary as a function of the polar angle, and also as a function of the characteristic length, time and convection velocity scales of the turbulence contained in the jet shear layer.
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Tone_Haystacking_AIAA_2009.pdf
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Published date: 2009
Additional Information:
AIAA 2009-3216
Venue - Dates:
15th AIAA/CEAS Aeroacoustics Conference (30th AIAA Aeroacoustics Conference), Miami, USA, 2009-05-11 - 2009-05-13
Identifiers
Local EPrints ID: 71516
URI: http://eprints.soton.ac.uk/id/eprint/71516
PURE UUID: 625e7e38-93eb-40c1-b85b-a06367bd803c
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Date deposited: 17 Feb 2010
Last modified: 14 Mar 2024 02:42
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Contributors
Author:
C.J. Powles
Author:
B.J. Tester
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