Evaluation of active flow control applied to wind turbine blade section

A feasibility study for implementing active flow control (AFC) methods to improve the performance of wind turbines was performed. The experimental effort investigated the impact of zero-mass-flux (ZMF) piezofluidic actuators attempting to control boundary layer separation from thick airfoils that are suitable for wind turbine rotor blades. It was demonstrated that the ZMF actuators can replace passive vortex generators that are commonly used for boundary layer separation delay, without the inherent drag penalty that the passive devices impose. It has been shown that ZMF fluidic actuators are suitable for flow control in wind turbine application due to the fact that they are adjustable for wider Reynolds number range, while vortex generators are tuned to perform well in one design point. It was demonstrated that AFC can effectively double the maximum lift of this airfoil at low Reynolds numbers. A possible application is a significant reduction of the turbine start-up velocity. It was also found that even for a contaminated blade, AFC is capable to delay the stall and decrease the drag using low energy expenditure, therefore restoring and even surpassing the clean airfoil performance. The effectiveness of the AFC method was examined using a newly defined aerodynamic figure of merit. Various scaling options for collapsing the effect of the excitation magnitude on the lift alternation due to the activation of zero-mass-flux periodic excitation for boundary layer separation control are proposed and examined using experimental data.