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Numerically solving the sound transmission in the intake of a turbofan engine with non-axisymmetric lining

Maas, B.J. (2014) Numerically solving the sound transmission in the intake of a turbofan engine with non-axisymmetric lining.

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Abstract:During the internship, a matlab code has been developed to test the feasability of a semi-analytical iterative method to calculate the sound propagation through the inlet duct of a turbo-fan engine in the presence of non-axisymmetric acoustic lining due to liner discontinuities such as liner splices and patches. The method is based on a Finite Element (FE) formulation of the problem and is an extension to existing FE methods. Four different stages exist within the code: the creation of a simple, structured computational mesh of an arbitrary duct shape; the solving of the one dimensional Helmholtz equation at the inlet and outlet cross-section of the duct mesh to describe the incident, reflected and transmitted sound wave modes; the solving of the two dimensional Helmholtz equations in the duct for axisymmetric lining and the inclusion of the iterative method to solve the set of coupled equations that comes into existence when describing a non-axisymmetric lining in terms of a Fourier expansion. The first three stages have been implemented succesfully, with the results of the 1D and 2D Helmholtz solvers validated against exact results for simple cases and data obtained from literature for more complex ones. The final stage was implemented succesfully up to the point that the iterative solver gives converging results according to expectations. Comparison of the data with an existing method however showed little agreement so far and more work is to be done.
Item Type:Internship Report (Master)
University of Southampton, United Kingdom
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:Sound transmission, non-axissymetric lining, Iterative numerical solver, finite element method, feasability study
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