Effective computation of acoustic propogation in turbofan aero-engine ducts
Effective computation of acoustic propogation in turbofan aero-engine ducts
In this thesis, a numerical matching (MM) procedure is applied to the acoustic analysis of turbofan intake and bypass ducts.
A revised MM procedure has been proposed in this research. It is different to the existing approach employed by Beckemeyer [1], Cummings [2] and Sijtsma [3] in their studies of duct acoustics. When flow is present in the duct, the revised MM procedure yields solutions which give better agreement with the finite element (FE) transmission analysis than those using the existing approach. When no flow in the duct, both approaches are equivalent. The research has shown that the revised MM scheme has correctly modelled a range of benchmark problems and converged to the correct solutions with a small number of duct modes. The research has also shown that the revised MM procedure is capable of studying sound diffraction by a splitter in the two-dimensional flow duct. The MM scheme also shows less computation times and storage requirement than the FE transmission analysis when applied to study a three-dimensional problem.
Issues regarding the computation of duct eigenvalues and eigenfunctions in the presence of uniform and sheared flows have also been addressed in the research. An FE eigenvalue model has been developed for calculating the eigenmodes in ducts of arbitrary cross-section and with non-uniform impedance boundaries and flow. The accuracy and convergence of the FE eigenvalue model has been extensively validated using the analytical solutions and the results in the literatures obtained by other methods. The effects of non-uniform mean flow and acoustic impedance boundaries on the modal sound field in a duct have been studied using the validated FE eigenvalue model. The study has also shown that using an interactive routine (ARPACK), sets of propagating eigenmodes can be obtained at modest computational cost for frequencies and flow conditions which are characteristics of turbofan intake and bypass ducts.
University of Southampton
Hii, Vincent Jiu Ta
78af2411-bafd-4186-8d1b-e87a2316e793
2005
Hii, Vincent Jiu Ta
78af2411-bafd-4186-8d1b-e87a2316e793
Hii, Vincent Jiu Ta
(2005)
Effective computation of acoustic propogation in turbofan aero-engine ducts.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
In this thesis, a numerical matching (MM) procedure is applied to the acoustic analysis of turbofan intake and bypass ducts.
A revised MM procedure has been proposed in this research. It is different to the existing approach employed by Beckemeyer [1], Cummings [2] and Sijtsma [3] in their studies of duct acoustics. When flow is present in the duct, the revised MM procedure yields solutions which give better agreement with the finite element (FE) transmission analysis than those using the existing approach. When no flow in the duct, both approaches are equivalent. The research has shown that the revised MM scheme has correctly modelled a range of benchmark problems and converged to the correct solutions with a small number of duct modes. The research has also shown that the revised MM procedure is capable of studying sound diffraction by a splitter in the two-dimensional flow duct. The MM scheme also shows less computation times and storage requirement than the FE transmission analysis when applied to study a three-dimensional problem.
Issues regarding the computation of duct eigenvalues and eigenfunctions in the presence of uniform and sheared flows have also been addressed in the research. An FE eigenvalue model has been developed for calculating the eigenmodes in ducts of arbitrary cross-section and with non-uniform impedance boundaries and flow. The accuracy and convergence of the FE eigenvalue model has been extensively validated using the analytical solutions and the results in the literatures obtained by other methods. The effects of non-uniform mean flow and acoustic impedance boundaries on the modal sound field in a duct have been studied using the validated FE eigenvalue model. The study has also shown that using an interactive routine (ARPACK), sets of propagating eigenmodes can be obtained at modest computational cost for frequencies and flow conditions which are characteristics of turbofan intake and bypass ducts.
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Published date: 2005
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Local EPrints ID: 465850
URI: http://eprints.soton.ac.uk/id/eprint/465850
PURE UUID: 0823ca81-684d-4ba6-a6e2-08309c6813fa
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Date deposited: 05 Jul 2022 03:17
Last modified: 16 Mar 2024 20:24
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Author:
Vincent Jiu Ta Hii
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