Aerodynamic performance of semi-submersible floating wind turbine under pitch motion

Abstract

Pitch motion is a critical factor that affects the aerodynamic load of blades and the motion response of the floating platform. To study the effects of pitch motion, the NREL 5-MW is analyzed by using Computational Fluid Dynamics (CFD) method. The motion of the wind turbine and the floating platform is dealt with dynamic fluid–solid interaction technology. The mesh in the blade rotation domain and the motion domain are sliding mesh and overlapped mesh respectively. The Fluid Volume Fraction (VOF) method is utilized to generate and track the free surface of the ocean wave. By setting the frequencies and amplitudes of sinusoidal pitch motion, the distributed aerodynamic pressure coefficient of the cross-sections is studied along the blade spanwise direction, and the instantaneous thrust, the turbine power coefficient and the wake vortex structure are analyzed. For blade only cases, results show that the pressure coefficient near the leading edge of each spanwise blade section reaches a maximum at the half-cycle, and the turbine power output is in phase with the pitch motion. For fully coupled cases, both the frequency of the turbine thrust and pitch motion is determined by the incident wave but in a reversed phase.