Effects of leading- and trailing-edge Gurney flaps on a delta wing

An experimental wind-tunnel investigation is undertaken to determine the ef fects of Gurney flaps on a 70-deg planar delta wing. Both upper- and lower- surface leading edge, as well as trailing-edge flaps are investigated. Resu lts are presented comprising force balance, on- and off-surface how visuali zation as well as flowfield surveys. The data indicate that the lower surfa ce leading-edge flaps increase the maximum lift coefficient and poststall l ifting ability. The trailing-edge Gurney flap shifts the zero-lift angle of attack negative, thereby increasing lift for a given angle of attack, and also increases the maximum and poststall lift coefficient. Both of these fl ap configurations improve the wing efficiency at moderate to high lift coef ficients. The devices do not greatly affect the longitudinal stability of t he wing, although the trailing-edge flap generates an increase in nose-down pitching moment. The lower-surface leading-edge flap causes a moderate del ay in the onset and progression of vortex breakdown over the wing. Upper su rface leading-edge flaps degrade performance.