Wind turbine blades experience unsteady aerodynamic loading under various off-design conditions. The fatigue loading reduces the operational time of the wind turbine hence leads to an increase in the Cost of Energy (CoE) of the wind power. In this study, active flow control with unsteady blowing actuators was applied to a two-dimensional wind turbine airfoil to alleviate the unsteady aerodynamic loading and improve the aerodynamic performance, particularly under large scale freestream disturbances. A low speed, open jet aeroacoustic wind tunnel was designed and constructed based on an existing anechoic chamber for this investigation. A theoretical analysis based on a Blade Element Momentum (BEM) algorithm was performed to evaluate the effect of flow control on the power output of the wind turbines. The result from the assessment indicates a 60% increase in operational range could be achieved with flow control. In addition, experimental investigations were carried out utilizing surface dynamic pressure sensors, a force balance and Particle Image Velocimetry (PIV) flow field measurement techniques. The results show that the fluctuating loading generated by an upstream cylinder wake was reduced by up to 12% using a proportional closed loop control algorithm at 27 degree angle of incidence. Under the same unsteady freestream conditions, the averaged lift coefficient at 19 degree angle of incidence was enhanced by up to 20% while the pressure drag coefficient was reduced by up to 10%.
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