Experimental studies on the drag reduction and lift enhancement of a delta wing

An experimental wind-tunnel investigation is undertaken to determine the effects of riblets and Gurney flaps on a 40-deg delta wing at a chord Reynolds number of 2.5 × 10⁵. The results show that riblets reduce the drag of the delta wing over a range of angle of attack; the V-shaped riblet with h = s = 0.2 mm has the most significant effect at an angle of attack of 6 deg. A drag reduction of 40% is obtained, and the corresponding lift-to-drag ratio is also a maximum with an increase of about 61% over the clean wing. On the other hand, in comparison with the baseline clean configuration, all Gurney flaps increase the lift coefficient. The best performance is obtained for the 1% chord Gurney flap, which yields a maximum lift-to-drag ratio at a 6-deg angle of attack; this provides an increase of 17.3% compared with the clean wing configuration. However, no favorable effects are found when the riblets and the Gurney flaps are used together.