This paper aims to simulate the motion of wind turbine and the swing rudder under wind direction change. Swing rudder is a rudder pivoted on the nacelle. The turbine with it shows good performance on yaw alignment under sudden wind direction change. However the efficiency of swing rudder is only evaluated by field operation that wind condition is hard to measure precisely. Thus the detailed mechanism of swing rudder is not sufficiently revealed. In order to evaluate the efficiency of Swing rudder, we simulated both the turbine model with swing rudder and with fixed rudder. The yawing motion is simulated using aeroelastic simulation code FAST developed by National Renewable Energy Laboratory. Numerical model of wind turbine is based on Zephyr Airdolphin GTO. In order to evaluate the efficiency of swing rudder, Simulation condition is set to be one wind direction change with steady wind speed. As a result, it is revealed that swing rudder reduces maximum yaw error when wind direction change is fast. Moreover, that characteristic is not dependent on magnitude of wind direction change. In addition, from the simulation with turbulent condition, the performance between swing rudder and fixed rudder is observed.
