Abstract
In this research, effects of Gurney flaps were investigated for aerodynamic characteristics of NACA4412 airfoil by wind-tunnel experiments. The Gurney flaps with height of 0 to 6% of the chord length were attached at the trailing edge. Under flow condition of Reynolds number 6.5×105, experimental setup was three-dimensional (3D) or quasi two-dimensional (2D), according to flow fields without or with side plates. The higher the Gurney flaps are, the more both maximum lifts and stall angles increase: in 2D cases maximum lifts become higher but stall angles hardly change, while in 3D cases stall angles become remarkably higher than in 2D cases. Each family of polar curves for 2D or 3D measurements constitutes a curve like an envelope. By use of each “envelope”, when the necessary value of lift is given, combination of an attack angle and a flap height with the lowest value of drag can be obtained.
