Numerical calculation of pressure modes at high frequencies in lined ducts with a shear flow
Numerical calculation of pressure modes at high frequencies in lined ducts with a shear flow
This paper describes an implementation of the standard Galerkin finite element method for the analysis of the acoustic and vortical modes in an axisymmetric lined duct carrying a high speed, subsonic, parallel mean shear flow. This is fundamentally theoretical work, but with a view to the specific engineering application of acoustic liner optimization in turbofan aero-engine ducts, as cylindrical and annular ducts are approximate models of inlet and bypass ducts, respectively. At high frequencies, the acoustic wavelength is comparable to the boundary layer thickness and this has an effect on acoustic refraction close to the duct walls. Preliminary results of this study reveal how different boundary layer profiles affect sound attenuation in a lined duct, compared with a uniform mean flow. The method solves the third-order eigenvalue problem for the pressure perturbation (Pridmore-Brown equation) with a locally reacting impedance boundary condition. The distinctive feature of this implementation is that it is fast and efficient. Owing to the circular geometry, the problem is reduced to a one-dimensional finite element solution, which permits at high frequencies the calculation of a large number of modes at a modest computational cost.
9781615676804
Olivieri, O.
ebe1ce34-3164-403b-8417-e2eb63f90821
McAlpine, A.
aaf9e771-153d-4100-9e84-de4b14466ed7
Astley, R.J.
cb7fed9f-a96a-4b58-8939-6db1010f9893
26 October 2009
Olivieri, O.
ebe1ce34-3164-403b-8417-e2eb63f90821
McAlpine, A.
aaf9e771-153d-4100-9e84-de4b14466ed7
Astley, R.J.
cb7fed9f-a96a-4b58-8939-6db1010f9893
Olivieri, O., McAlpine, A. and Astley, R.J.
(2009)
Numerical calculation of pressure modes at high frequencies in lined ducts with a shear flow.
8th European Conference on Noise Control 2009 (EURONOISE 2009), Edinburgh, United Kingdom.
26 - 28 Oct 2009.
10 pp
.
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Conference or Workshop Item
(Paper)
Abstract
This paper describes an implementation of the standard Galerkin finite element method for the analysis of the acoustic and vortical modes in an axisymmetric lined duct carrying a high speed, subsonic, parallel mean shear flow. This is fundamentally theoretical work, but with a view to the specific engineering application of acoustic liner optimization in turbofan aero-engine ducts, as cylindrical and annular ducts are approximate models of inlet and bypass ducts, respectively. At high frequencies, the acoustic wavelength is comparable to the boundary layer thickness and this has an effect on acoustic refraction close to the duct walls. Preliminary results of this study reveal how different boundary layer profiles affect sound attenuation in a lined duct, compared with a uniform mean flow. The method solves the third-order eigenvalue problem for the pressure perturbation (Pridmore-Brown equation) with a locally reacting impedance boundary condition. The distinctive feature of this implementation is that it is fast and efficient. Owing to the circular geometry, the problem is reduced to a one-dimensional finite element solution, which permits at high frequencies the calculation of a large number of modes at a modest computational cost.
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Olivieri_2009.pdf
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Published date: 26 October 2009
Venue - Dates:
8th European Conference on Noise Control 2009 (EURONOISE 2009), Edinburgh, United Kingdom, 2009-10-26 - 2009-10-28
Identifiers
Local EPrints ID: 79111
URI: http://eprints.soton.ac.uk/id/eprint/79111
ISBN: 9781615676804
PURE UUID: ef76f5ea-8892-43a1-a8f3-75b55f53237f
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Date deposited: 18 Mar 2010
Last modified: 14 Mar 2024 02:42
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Author:
O. Olivieri
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