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Application of a high-order FEM solver to realistic aeroengine exhaust noise radiation

Application of a high-order FEM solver to realistic aeroengine exhaust noise radiation
Application of a high-order FEM solver to realistic aeroengine exhaust noise radiation
For many industries the propagation of sound in complex flows is a critical issue. Most Computational
Aero Acoustics propagation methods currently in use in industry are based on the full potential
theory which cannot properly describe sound propagation through complex sheared flows.
When dealing with turbomachinery noise radiated from the engine exhaust, a strong refraction
occurs through the jet shear layer. To better represent the physics at hand one can solve instead
the Linearised Euler Equations (LEE). However, time-domain LEE models have shortcomings for
industrial applications, such as the presence of linear instabilities and the stability of impedance
models. Most of these issues can be avoided by solving the LEE in the frequency domain. Nevertheless,
this can be very demanding because of the high memory requirements associated with
solving large sparse linear systems. For high frequency, the standard finite element method (FEM)
is known to suffer from large dispersion errors. Its straightforward application to the LEE, which
involve up to five unknowns in 3D, would be computationally costly. To address these issues,
an alternative approach based on high-order FEM is presented in this paper. A discretised axisymmetric
form of the LEE is described in conjunction with Perfectly Matched Layers. In addition,
a numerical stabilisation scheme of type Galerkin/Least-Squares is included in the numerical
model. The proposed method is applied to the propagation of duct modes inside a turbofan engine
exhaust, with complex geometry and non-uniform mean flow. The sound propagation and
radiation are accurately described, as well as the interaction between the acoustic waves and the
hydrodynamic field resulting in the vorticity shedding from the duct lips
1278-1285
Curran Associates
Hamiche, K.
0f3238e5-91de-485c-922d-057c9a133201
Gabard, G.
bfd82aee-20f2-4e2c-ad92-087dc8ff6ce7
Bériot, H.
d73aea9a-8247-493f-9603-e76dc60e99ba
Crocker, Malcolm J.
Pedrielli, Francesca
Luzzi, Sergio
Pawelczyk, Marek
Carletti, Eleonora
Hamiche, K.
0f3238e5-91de-485c-922d-057c9a133201
Gabard, G.
bfd82aee-20f2-4e2c-ad92-087dc8ff6ce7
Bériot, H.
d73aea9a-8247-493f-9603-e76dc60e99ba
Crocker, Malcolm J.
Pedrielli, Francesca
Luzzi, Sergio
Pawelczyk, Marek
Carletti, Eleonora

Hamiche, K., Gabard, G. and Bériot, H. (2015) Application of a high-order FEM solver to realistic aeroengine exhaust noise radiation. Crocker, Malcolm J., Pedrielli, Francesca, Luzzi, Sergio, Pawelczyk, Marek and Carletti, Eleonora (eds.) In 22nd International Congress on Sound and Vibration 2015 (ICSV 22). Curran Associates. pp. 1278-1285 .

Record type: Conference or Workshop Item (Paper)

Abstract

For many industries the propagation of sound in complex flows is a critical issue. Most Computational
Aero Acoustics propagation methods currently in use in industry are based on the full potential
theory which cannot properly describe sound propagation through complex sheared flows.
When dealing with turbomachinery noise radiated from the engine exhaust, a strong refraction
occurs through the jet shear layer. To better represent the physics at hand one can solve instead
the Linearised Euler Equations (LEE). However, time-domain LEE models have shortcomings for
industrial applications, such as the presence of linear instabilities and the stability of impedance
models. Most of these issues can be avoided by solving the LEE in the frequency domain. Nevertheless,
this can be very demanding because of the high memory requirements associated with
solving large sparse linear systems. For high frequency, the standard finite element method (FEM)
is known to suffer from large dispersion errors. Its straightforward application to the LEE, which
involve up to five unknowns in 3D, would be computationally costly. To address these issues,
an alternative approach based on high-order FEM is presented in this paper. A discretised axisymmetric
form of the LEE is described in conjunction with Perfectly Matched Layers. In addition,
a numerical stabilisation scheme of type Galerkin/Least-Squares is included in the numerical
model. The proposed method is applied to the propagation of duct modes inside a turbofan engine
exhaust, with complex geometry and non-uniform mean flow. The sound propagation and
radiation are accurately described, as well as the interaction between the acoustic waves and the
hydrodynamic field resulting in the vorticity shedding from the duct lips

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Accepted/In Press date: 7 February 2015
Published date: November 2015
Venue - Dates: 22nd International Congress on Sound and Vibration ICSV22, Italy, 2015-07-12 - 2015-07-16
Organisations: Acoustics Group

Identifiers

Local EPrints ID: 381495
URI: https://eprints.soton.ac.uk/id/eprint/381495
PURE UUID: b855d5b4-718f-40d1-8985-00a1094145d0

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Date deposited: 06 Oct 2015 14:25
Last modified: 19 Jul 2019 17:19

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