Numerical Investigation on the Effect of Adding a Gurney Flap with Multiple Heights on the Aerodynamic Performance of Various Cambered Airfoils

Computational fluid dynamics simulations were used to investigate the effect on the aerodynamic characteristics by adding Gurney flaps with multiple heights to various cambered airfoils that are currently used in general aviation aircraft. The investigated aerodynamic characteristics were the lift and drag coefficients, lift-to-drag ratio, and surface pressure distribution. The investigated airfoils (in two dimensions) were NACA 0012, NACA 2412, NACA 4412, NACA 6409, and NACA 23014. The used Gurney flap heights were 1 and 1.5% of the chord length. The investigation was conducted using a chord Reynolds number of \(2 \times {10}^{6}\) . The results show that the implementation of a 1% chord length Gurney flap had increased the maximum lift of all of the investigated airfoils, but it also resulted in a drag penalty. However, at low to moderate angles of attack, the increase in lift outcomes the increase in drag, which as a result, increases the lift-to-drag ratio. Hence, improving the performance of the airfoils. The results also show that increasing the camber of the airfoil, i.e. from NACA 0012 airfoil to NACA 6409 airfoil, had decreased the percent increase in the lift-to-drag ratio at low to moderate angles of attack, which indicates that the Gurney flap is more effective when used in low cambered airfoils. Increasing the size of the flap to 1.5% chord length led to a further increase in both maximum lift and drag penalty. However, the increase in drag was high enough to overcome the increase in lift. As such, the overall performance enhancement was lower than that of the 1% chord length Gurney flap for all of the investigated airfoils.