Research on the effect of yawing motion on tidal turbine performance based on actuator-line method

An actuator line method (ALM) code is used to investigate the yaw motion of tidal stream turbines, using different induced frequencies, amplitudes and starting angles. The relative velocity in the ALM calculation is corrected by considering the reaction force of the water on the floating tidal turbine. Because the ALM directly converts the flow velocity characteristics on the mesh element into the force characteristics, more small-scale and high-frequency signals appear, compared to Blade-Resolved Method simulations. In the results, the oscillation frequency of power coefficient and thrust coefficient (Cp, Ct) is twice of the yawing motion frequency when the starting yaw angle is 0°. Increasing the yawing amplitude as well as the starting angle both lower the mean values of Cp and Ct whilst the effect of frequency is slight. The turbine's hydrodynamic coefficients are obtained by best-fit model. The yawing amplitude has a moderate effect on the constant hydrodynamic terms.