Coupled experimental-numerical analysis of energy harvesting dynamics of tidal stream turbine: Synergistic effects of operational status and morphological evolution in wave-current environments

Tidal stream turbine operational status and its induced morphological evolution critically impact energy conversion performance under coupled waves and currents, yet this remains understudied. This study aims to investigate synergistic effects of operational status and morphological evolution on the energy harvesting dynamics of horizontal-axis tidal stream turbines (HATST) in wave-current environments. A coupled experimental-numerical analysis framework was established. The mono-pile supported HATST induced equilibrium scour morphology was digitally reconstructed according to experimental results. This digital reconstruction was used to establish immersed boundary modeled scour seabed in the numerical model. The actuator line method modeled HATST was implemented to extract the power and thrust coefficients (Cp and Ct). The variations of Cp and Ct after scour under varying tip speed ratio (TSR), yaw angle, or tip-bed clearance were analyzed. The results indicate that under wave-current loading, the variations of mean values of Cp and Ct after scour are less than 3.50 % and 2.50 % when TSR doesn't exceed its optimal value. The mean values of Cp and Ct decline by more than 4.50 % and 2.50 % after scour when TSR exceeds its optimal value. Under yaw angle exceeding 15°, the mean values of Cp and Ct can decline by over 0.92 % and 0.16 % after scour. Under tip-clearance exceeding 2.5 times of pile diameter, the Cp and Ct reduce after scour. Otherwise, the tip-bed clearance not exceeding 2.5 times of pile diameter can restrain the reductions of Cp and Ct after scour