Contributions to the mathematical modelling of unsteady aerodynamics and aeroacoustics using indicial theory

Leishman, John Gordon (2002) Contributions to the mathematical modelling of unsteady aerodynamics and aeroacoustics using indicial theory. DSc thesis, University of Glasgow.

Abstract

Helicopter rotor blades encounter complex, time-varying changes in aerodynamic angle of attack, which result from many interdependent sources of excitation. These sources can produce unsteady aerodynamic problems that are difficult to predict, and may include effects associated with simultaneous time-variations in angle of attack and onset flow velocity, the effects of the rotor wake induced velocity field and blade vortex interactions, and also dynamic stall. The successful design of advanced helicopters with better aerodynamic performance and lower noise requires the ability to confidently predict the unsteady aerodynamic forces on the rotor system. To this end, the objective of this dissertation is to present a body of work on the modelling of unsteady aerofoil behaviour. The work contributes to the theory and understanding of unsteady aerofoil flows in general, and to the aerodynamic and aeroacoustic predictive capabilities of helicopter rotor analyses, in particular. The ultimate goal is to be able to better model unsteady aerodynamic and aeroacoustic effects accurately on the rotor, and in an appropriate computationally efficient mathematical form that is compatible with the entire helicopter rotor analysis. To meet these goals, the work presented in this dissertation shows that the indicial method provides for an excellent and computationally efficient mathematical representation of unsteady aerofoil behaviour. The results show that indicial method has good applicability for a wide range of practical flow situations and time-dependent forcing conditions likely to be encountered by helicopter rotors. Both experimental measurements and results from other aerodynamic methods were used to validate the indicial approach, both indirectly and directly. It was shown, by means of key examples, how the linearity of the indicial method and the principles of Duhamel superposition can be justified for many problems of practical significance. (Abstract shortened by ProQuest.).

• Item Type: Thesis (DSc)
• Qualification Level: Doctoral
• Additional Information: Adviser: Bryan Richards.
• Keywords: Aerospace engineering
• Colleges/Schools: College of Science and Engineering
• Date of Award: 2002
• Depositing User: Enlighten Team
• Unique ID: glathesis:2002-71060
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 10 May 2019 10:49
• Last Modified: 08 Aug 2022 12:36
• Thesis DOI: 10.5525/gla.thesis.71060
• URI: https://theses.gla.ac.uk/id/eprint/71060