Influence of Flap Parameters on the Aerodynamic Performance of a Wind-Turbine Airfoil

A numerical method has been used to analyze the flow field related to a NACA 0015 airfoil with and without a flap and assess the influence of the flap height and angle on the surface pressure coefficient, lift coefficient, and drag coefficient. The numerical results demonstrate that the flap can effectively improve the lift coefficient of the airfoil; however, at small attack angles, its influence is significantly reduced. When the angle of attack exceeds the critical stall angle and the flap height is 1.5% of the chord length, the influence of the flap becomes very evident. As the flap height increases, the starting point of the separation vortex gradually moves forward and generates a larger wake vortex. Optimal aerodynamic characteristics are obtained for 1.5% (of the chord length) flap height and a 45 degrees flap angle; in this case, the separation vortex is effectively reduced.