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Lak, Saman

University of British Columbia

Tip vortex cavitation (TVC) is a complex phenomenon that occurs during the operation of marine propellers, contributing to the underwater radiated noise (URN) of marine vessels. The urgent need for alleviation of the URN levels of marine vessels due to its detrimental impact on marine ecosystems necessitates a thorough investigation of this phenomenon and development of mitigation strategies. In this thesis, due to the challenges associated with the numerical simulation of this phenomenon, a comprehensive validation of large eddy simulation of tip vortex cavitating flow past a hydrofoil is conducted, followed by a detailed analysis of the oscillatory dynamics of TVC and its contribution to the near-field pressure fluctuations. In the next stage, geometric modifications of bending and twisting types are proposed and studied as a strategy for the mitigation of tip vortex cavitation. An investigation of modified hydrofoils in various bending and twisting configurations is conducted demonstrating the potential of these strategies for TVC mitigation without adversely affecting the hydrodynamic performance. A detailed analysis of the flow field in various modified configurations is carried out to reveal the mechanisms involved in the TVC mitigation achieved through these geometric modifications. The thesis is concluded with the development of a toolbox for the application of chord-normal bending and twisting modifications to marine propellers. Preliminary simulations of flow past a conventional and a modified propeller are conducted, which demonstrate that the TVC mitigation strategies proposed in the present work are promising methods for reducing the footprints of human activities on the ocean soundscape.

Text

2024-12-19

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89936

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/