EXPERIMENTAL-STUDY OF LIFT-ENHANCING TABS ON A 2-ELEMENT AIRFOIL

The results of a wind-tunnel test are presented for a two-dimensional NACA 63(2)-215 Mod B airfoil with a 30% chord single-slotted flap. The use of lift-enhancing tabs (similar to Gurney naps) on the lower surf ace near the trading edge of both elements was investigated on four fl ap configurations. A combination of vortex generators on the flap and lift-enhancing tabs was also investigated. Measurements of surface-pre ssure distributions and wake profiles were used to determine the aerod ynamic performance of each configuration. BS reducing flow separation on the flap, a lift-enhancing tab at the main-element trailing edge in creased the maximum lift by 10.3% for the 42-deg flap case. The tab ha d a lesser effect at a moderate flap deflection (32 deg) and adversely affected the performance at the smallest nap deflection (22 deg). A t ab located near the flap trailing edge produced an additional lift inc rement for all flap deflections. The application of vortex generators to the nap eliminated lift-curve hysteresis and reduced flow separatio n on two configurations with large flap deflections (>40 deg). A maxim um-lift coefficient of 3.32 (17% above the optimum baseline) was achie ved with the combination of lift-enhancing tabs on both elements and v ortex generators on the flap.