Hydrodynamic analysis and fatigue loading evaluation of tidal turbine rotor blades

Many studies have revealed that tidal turbines are subject to frequent and large-scale hydrodynamic loading fluctuations in the ocean environment, particularly in floating and shallow-water installations, where waves and inflow turbulence dominate. These unsteady loads may lead to fatigue damage of the blades being loaded. Thus, the fatigue loading on tidal turbines needs to be accurately evaluated within the design stage. To investigate the hydrodynamic performance of tidal turbines under ocean flows, three-dimensional computational fluid dynamics models of a horizontal-axis tidal turbine rotor have been developed. Notable thrust variation on turbine rotor blades induced by current turbulence is observed with inflow profiles with depth-varying and time-varying velocities. Afterwards, a three-dimensional numerical wave tank model has been developed, and then combined with the developed tidal turbine model to investigate the fatigue loadings on a tidal turbine under waves. The model was validated against physical experiments and then extended to combined wave–current inflow conditions to systematically assess the hydrodynamic loads on turbine rotor blades. The fatigue loading on turbine rotor blades can be significantly increased with the addition of the influence of surface waves to tide currents. In parallel, a series of hydrodynamic tests has been conducted on a stationary tidal turbine model in a physical wave tank. The hydrodynamic loadings on the turbine and the blockage effect at different submergence depths under various wave conditions have been systematically investigated. The results show that turbine thrust decreases with increasing submergence depths and wave periods under intermediate-depth water conditions. The analysis was further expanded to twin-turbine tests with different orientation angles, and the results demonstrate that stronger array interactions lead to higher turbine loads. In conclusion, this thesis systematically analyses tidal turbines and evaluates the fatigue loadings on turbine rotor blades under complex inflow conditions. The research can help gain a better knowledge of the turbine-fluid interaction, improve fatigue design and support the development of tidal energy. In the long run, this research can help society achieve sustainable development goals and support progress toward net-zero CO₂ targets.

Funder

Taighde Éireann - Research Ireland

Publisher

University of Galway

Rights

CC BY-NC-ND

cbn

Collections

University of Galway Theses (PhD Theses)