This paper describes about the unsteady flow field and the unsteady aerodynamic loads of a horizontal axis wind turbine in yawed flow condition. As the use of large-scale commercial wind turbines is expanded over the world, the wind turbine industry is facing many difficulties in consulting efficient wind turbine machines, which is caused by the inability to adequately predict structural loading and power output. Since the wind turbines are operating in the natural environment, turbines are always subjected to unsteady nature. However, recognizing on aerodynamics of wind turbine associated with three-dimensional, unsteady and separated complex flow is not sufficient. When incoming flow into the rotor plane is obliquely to the rotor plane which is called yawed flow condition, due to the rapid and periodical change of the local angle of attack to the rotor blade, the dynamic load to the rotor is excited by the dynamic stall effect. In this study to clarify the relationship of dynamic loads and velocity field around the rotor blade excited by dynamic stall vortices in yawed flow conditions, near wake velocity field and blade-root flapwise bending moment have been measured synchronously.

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