Effect of platform roll motion on aerodynamic performance of floating offshore wind turbine under yawed conditions

This study investigates the unsteady aerodynamics of a yawed floating offshore wind turbine (FOWT) undergoing platform roll motion using the free vortex wake method. The thrust and power coefficients are systematically examined under various roll amplitudes, frequencies, and yaw angles. Through the analysis of the angle of attack (AOA) under this condition, a key finding is the proposal of the Equal-AOA radius (Formula presented), which is defined as the radial location where the AOA equals that under the fixed-platform yawed condition. This radius provides insight into the effect of roll motion on the angle of attack under yawed conditions. The expression for this radius is derived, and its properties are examined. Roll-induced wake structure changes tend to enlarge this radius on the downwind side and reduce it on the upwind side. Additionally, at maximum roll positions, dynamic wake effects are observed to induce an antisymmetric AOA distribution across the rotor plane, and under large yaw angles, blade-wake interaction may contribute to a localized increase in the angle of attack. These findings provide useful references for the load control and wake management of offshore wind farms, and the proposed Equal-AOA radius (Formula presented) can assist in pitch control design for yawed FOWT under roll motion.