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Analysis of vortex-lifting surface interactions

Thom, Alasdair D. (2011) Analysis of vortex-lifting surface interactions. PhD thesis, University of Glasgow.

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Abstract

The interaction of a vortex with a lifting surface occurs in many aerodynamic systems, and can induce significant airloads and radiate impulsive noise. Yet due to their complex nature, the ability to accurately model the important flow physics and noise radiation characteristics of these interactions in realistic situations has remained elusive. This work examines two cases of vortex-lifting surface interactions by enhancing the capabilities of a high fidelity flow solver. This flow solver utilises high spatial discretisation accuracy with a 5th order accurate WENO scheme, and overset meshes to accurately resolve the formation, evolution and interaction of a tip vortex using an inviscid approximation of the fluid. An existing computational infrastructure is further developed and applied to analyse blade-vortex interactions that occur on a helicopter rotor. An idealised interaction is studied, where an independently generated vortex interacts with a rotor. It is found that through the employment of adequate spatial and temporal resolution, the current methodology is capable of resolving the important details of the interaction over a range of vortex-blade miss distances. A careful study of the spatial and temporal resolution requirements is conducted to ensure that the computed results converge to the correct physical solution. It is also demonstrated that a linear acoustic analysis can accurately predict the acoustic energy propagated from these interactions to the far-field, provided the blade surface pressures are accurately computed. The methodology is then used to study an idealised propeller wake-wing interaction, which occur behind a tractor mounted turboprop. A computationally efficient method of modelling the wake-wing interaction is developed and the computed surface pressures of the interaction are confirmed to agree well with the experimental data. The analysis is coupled to an optimisation algorithm to determine a novel wing design, and it is found that significant drag reductions can be achieved with small changes in the twist distribution of the wing. This work confirms that by using a combination of strategies including efficient grids, high order accurate numerical discretisations and a flexible software infrastructure, high fidelity methods can indeed be used to accurately resolve practical cases of vortex-lifting surface interactions in detail while being feasible in a design setting. The airloads and aeroacoustics from these interactions can be accurately predicted, thus confirming that with the modern advances in computing and algorithms, high fidelity methodologies such as those presented in this thesis are in a position to be used to gain a deep understanding of the relevant flow physics and noise radiation patterns, and their impact on aircraft design.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Aerodynamics, fluid dynamics, acoustics, aeroacoustics, CFD, computational fluid dynamics, BVI, blade-vortex interaction, WENO schemes, weighted essentially non-oscillatory schemes, stencil walking scheme, dual time stepping scheme, finite volume scheme, vortex-surface interactions, vortex cutting, vortex bending, propeller wake-wing interaction, wing/blade optimisation, parallel computing, overset meshes, tip vortex formation, vortex convection
Subjects: T Technology > TL Motor vehicles. Aeronautics. Astronautics
Colleges/Schools: College of Science and Engineering > School of Engineering > Aerospace Sciences
Supervisor's Name: Duraisamy, Prof. Karthik and Marco, Dr. Vezza
Date of Award: 2011
Depositing User: Mr Alasdair Thom
Unique ID: glathesis:2011-3037
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Nov 2011
Last Modified: 10 Dec 2012 14:03
URI: http://theses.gla.ac.uk/id/eprint/3037

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