Experimental Study of Lift-Enhancing Tabs on a Two-Element Airfoil

Bruce L. Storms*Sterlin X So['tware, Palo Alto, ('al([brnia 04303andJames C. Ross+NASA Ames Research Center, Moffett Field, Cahfornia 94035-I000The results of a wind-tunnel test are presented for a two-dimensional NACA 632-215 Mod B airfoil with a30% chord single-slotted flap. The use of lift-enhancing tabs (similar to Gnrney flaps) on the lower surface nearthe trailing edge of both elements was investigated on four flap configurations. A combination of vortex generatorson the flap and lift-enhancing tabs was also investigated. Measurements of surface-pressure distributions andwake profiles were used to determine the aerodynamic performance of each configuration. By reducing flowseparation on the flap, a lift-enhancing tab at the main-element trailing edge increased the maximum lift hy10.3% fi)r the 42-deg flap case. ]'he tab had a lesser effect at a moderate flap deflection 132 deg) and adverselyaffected the performance at the smallest flap deflection (22 degL A tab h_ated near the flap trailing edgeproduced an additional lift increment for all flap deflections. The application of vortex generators to the flapeliminated li_curve hysteresis and reduced flow separation on two configurations with large flap deflections(>40 degt. A maximum-lift coefficient of 3.32 (17% above the optimum ba_lineJ was achieved with the com-bination of lift-enhancing tabs on both elements and vortex generators on the flap.Nomenclature(',, = section drag coefficient, d/qc(', = section lift coefficient, I/qc(',,, = section pitching-momentcoefficient, m/qc:('v = pressure coefficient, (p - p.)/qc = reference airfoil chordd = section dragd, = distance from tab to trailingedgeg = flap gapIt = heightL/D = lift-to-drag ratio/ = section liftm = section pitching momento/ -- flap overlapp = static pressureq = dynamic pressure. I/2pV-"Re = Reynolds numberV = freestream velocityat = angle of attack6 = deflection anglep = density of air