2011 年 6 巻 3 号 p. 333-341
The aerodynamic performance of a wind turbine depends on operating conditions such as tip speed ratio and pitch settings. Generally, the wind turbine blade shapes are designed based on two-dimensional airfoil characteristics which are measured under static conditions in terms of angle of attack. However, wind turbines operated under complex condition in field environment, frequently experiencing suddenly fluctuation of wind direction and velocity. It causes fluctuations of angle of attack for the blade element. Therefore, the clarification of airfoil characteristics under dynamic conditions is important for accurate estimation of the power output and aerodynamic loads on wind turbine. In this study, wind tunnel experiments under dynamic and static conditions for different turbulence intensities are conducted for a wind turbine airfoil. As the result, the lift coefficient for dynamic condition shows the hysteresis loop when the range of angle of attack during the pitching motion includes the stall angle. The flow turbulence changes the stall characteristics of the airfoil. The size of hysteresis loop depends on the stall characteristics and the range of pitching motion.