Effects of Leading- and Trailing-Edge Gurney Flaps on a Delta Wing

An experimental wind-tunnel investigation is undertaken to determine the effects of Gurney e aps on a 70-deg planar delta wing. Both upper- and lower-surface leading-edge, as well as trailing-edge e aps are investigated. Results are presented comprising force balance, on- and off-surface e ow visualization as well as e owe eld surveys. The data indicate that the lower surface leading-edge e aps increase the maximum lift coefe cient and poststall lifting ability. Thetrailing-edgeGurney e ap shifts the zero-liftangle of attack negative, thereby increasing lift for a givenangleofattack,and also increasesthemaximumand poststallliftcoefe cient.Both ofthesee apcone gurations improve the wing efe ciency at moderate to high lift coefe cients. The devices do not greatly affect the longitudinal stability of the wing, although the trailing-edge e ap generates an increase in nose-down pitching moment. The lower-surface leading-edge e ap causes a moderate delay in the onset and progression of vortex breakdown over the wing. Upper surface leading-edge e aps degrade performance.