Effect of Gurney Flaps on an Elliptical Airfoil

A low-speed wind tunnel investigation is presented characterizing the impact of Gurney flaps on an elliptical airfoil. The chordwise attachment location and height of the flaps were varied, as was the Reynolds number. The results showed strong nonlinearities in the lift curve which were present for all tested geometries. Flap effectiveness was seen to diminish as the flap was moved closer to the trailing edge stemming from flap submersion in separated flow. For the tested cases, the measured lift coefficients showed a weak Re dependency. The upper airfoil surface was shown to carry approximately 80% of the total lift load. The top surface caused a pitching moment reversal associated with nonlinearity in the lift curve.