Advanced rotor blade design based on high-fidelity computational fluid dynamics

Fitzgibbon, Thomas Alexander (2021) Advanced rotor blade design based on high-fidelity computational fluid dynamics. PhD thesis, University of Glasgow.

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This thesis is aimed at expanding the current state of the art in rotor design by combining high fidelity CFD and optimisation methods. Such methods are associated with extremely high computational costs, when optimisation of unsteady flow fields is required such as those encountered by a rotor in forward flight. For this reason, the majority of studies in literature resort to lower fidelity models for forward flight optimisation. To maintain the high fidelity of the Navier-Stokes equations at modest computational costs, an optimisation framework based on an overset adjoint harmonic balance method was developed within the present research, which is the primary novelty of the thesis. Firstly, however, the CFD solver is validated for a range of rotor designs in hover and forward flight, by comparing the performance predictions with available experimental data, and thereby verifying the findings obtained in the rotor design study. The CFD validation also includes a sensitivity analysis of various numerical modelling parameters on the performance predictions including effects of computational setup, grid resolution and turbulence models. The validation studies highlighted the need for more accurate and higher quality experimental data. Based on the CFD validation results, the use of standard performance metrics such as figure of merit and lift-to-drag ratio was assessed for comparing different rotor designs, showing that a dimensional thrust and torque comparison is more informative. A blade solidity study was also performed to inform the correct use of different solidity parameters, in particular, thrust- weighted solidity. The comparison of the different designs used for CFD validation highlighted the subtle aerodynamics involved in advanced planform shapes and the need for numerical optimisation.
The developed optimisation framework was applied to the AH-64A rotor blade and showed that significant performance benefits are available through blade planform shape modifications. The final design was validated in hover and forward flight using time-marching calculations. The differences between the harmonic balance and time-marching simulations are analysed in detail along with the sources behind the performance gains for the optimised blade. Finally, a discussion of the favourable rotor design features is conducted along with suggestions for improvements of the optimisation framework.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: T Technology > T Technology (General)
Colleges/Schools: College of Science and Engineering > School of Engineering > Autonomous Systems and Connectivity
Supervisor's Name: Barakos, Prof. George
Date of Award: 2021
Depositing User: Mr Thomas Fitzgibbon
Unique ID: glathesis:2021-81932
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 27 Jan 2021 09:15
Last Modified: 27 Jan 2021 09:22
Thesis DOI: 10.5525/gla.thesis.81932
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