Hydrodynamic analysis of vertical-axis tidal current turbine with surging and yawing coupled motions

Abstract The hydrodynamic performance of the rotated vertical-axis tidal current turbine with another two (i.e. surge and yaw in this paper) degrees of freedom (DOF) coupled motion in unbounded uniform flow is analysed by the dynamic mesh. The effects of the turbine's hydrodynamic loads have been studied and illustrated considering the 3-DOF coupled motion. Numerical results show that: 1) the effects of the hydrodynamic load is mainly caused by the surging motion, but the effects of the yawing motion is reflected when its frequency is greater than that of the surging; 2) There are fluctuations in the envelope curves of the thrust and lateral force, rotational and yawing moment coefficients of the turbine, and the fluctuation amplitudes have a positive correlation with the surging and yawing motion frequencies; 3) the calculation formula of the turbine's hydrodynamic loads coefficients are obtained. The results of the hydrodynamic loads calculated by the formulations and CFD numerical simulation show good agreements, which verify the calculation formulas reasonably. The results of this research can provide relevant data for the hydrodynamic analysis of turbines with multi-degree of freedom motion and the structural design.