SEPARATION CONTROL ON HIGH-LIFT AIRFOILS VIA MICRO-VORTEX GENERATORS

An experimental investigation has been conducted to evaluate boundary- layer separation control on a two-dimensional single-flap, three-cleme nt, high-lift system at near-flight Reynolds numbers with small surfac e-mounted vortex generators. The wind-tunnel testing was carried out i n the NASA Langley Low-Turbulence Pressure Tunnel as part of a coopera tive program between McDonnell Douglas Aerospace and NASA Langley Rese arch Center to develop code validation data bases and to improve physi cal understanding of multielement airfoil flows. This article describe s results obtained for small (subboundary-layer) vane-type vortex gene rators mounted on a multielement airfoil in a landing configuration. M easurements include lift, drag, surface pressure, wake profile, and fl uctuating surface heat fluxes. The results reveal that vortex generato rs as small as 0.18% of reference (slat and flap stowed) wing chord (' 'micro-vortex generators'') can effectively reduce boundary-layer sepa ration on the flap for landing configurations. Reduction of nap separa tion can significantly improve performance of the high-lift system by reducing drag and increasing lift for a given approach angle of attack . At their optimum chordwise placement on the flap, the micro-vortex g enerators are hidden inside the wing when the nap is retracted, thus e xtracting no cruise drag penalty.