Loading and Blade Deflection of a Tidal Turbine in Waves

A coupled numerical model has been developed and validated to study the fluid–structural interaction responses of a three-bladed tidal turbine in aligned waves and current. The unsteady blade element momentum (BEM) theory was combined with modal analysis for hydro-elastic calculation. Both the loading and deflection of the blade were studied. The dynamic loading on the blade due to structural deformation was much smaller than the wave-induced loading under linear wave conditions for the given condition. The linear response amplitude operators (RAOs) of the loads and the blade tip deflections were obtained and used to predict the linear responses. Although both sum- and difference-frequency responses can be identified from time domain simulations, the wave-induced load and the deflection of the blade are dominated by the first-order contributions. The maximum deflection of the blade tip could reach 1.3 m (203% of the means) in the flapwise direction and 0.35 m (210% of the mean) in the edgewise direction with a wave peak period of 11.3 s and a significant wave height of 5.5 m.