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Title: Aerodynamic and aeroacoustic modelling of engine fan broadband noise
Author: Gea-Aguilera, Fernando
ISNI:       0000 0004 6347 8319
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2017
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This thesis investigates simplified but representative configurations of the fan wake-OGV interaction noise, which is a major source of engine fan broadband noise during take-off and landing. To this end, Computational AeroAcoustics (CAA) simulations are performed by using the Linearised Euler Equations (LEEs) and synthetic turbulence methods. An advanced digital filter method is presented to generate divergence-free synthetic turbulence with explicit control on the resulting turbulence spectrum. The method, which is based on the Random Particle-Mesh (RPM) method and synthetic eddy methods, is able to produce two- and three-dimensional fluctuating velocity fields of homogeneous isotropic and anisotropic turbulence. It is also shown that similar levels of simulation accuracy can be achieved by using digital filter and Fourier mode methods. Nevertheless, the advanced digital filter method provides enhanced performance in terms of computational cost (up to 3:9 times faster for two-dimensional simulations in this study). CAA simulations using the advanced digital filter method are performed to improve current understanding of leading edge noise from single aerofoils. For example, the method is used to examine the distortion of turbulent structures in the leading edge region. Furthermore, a comparison between numerical and experimental noise measurements in open-jet wind tunnel experiments indicate that the advanced digital filter method is capable of reproducing experimental results with an accuracy to within 3 dB. This thesis also presents a parameter study to assess the effects of moderately anisotropic turbulence, as occurs in the fan wakes, on leading edge noise from single aerofoils. Finally, fan wake modelling assumptions, such as cyclostationary variations in turbulent kinetic energy and integral length scale, are investigated using a cascade of thin aerofoils. Results indicate that broadband noise mainly depends on the circumferentially-averaged spectrum that is perceived by the cascade, and not on the instantaneous features of the fan wakes. A parameter study on cascade noise using isotropic turbulence is also included in this thesis, where variations in the vane count, aerofoil thickness, camber, mean flow Mach number, stagger angle, and inter-vane spacing are investigated. It is confirmed that the flat plate assumption provides sufficient accuracy for the frequency range in which engine fan broadband noise is relevant.
Supervisor: Zhang, Xin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available