Design and Testing of a Winglet Airfoil for Low-Speed Aircraft

Abstract

The PSU 94-097 airfoil has been designed for use on winglets of high-performance sailplanes. The design problem is difficult because the airfoil must operate over a wide range of Reynolds numbers, and this range includes values that are relatively low. To validate the design tools, as well as the design itself, the airfoil was tested in the Penn State Low-Speed, Low-Turbulence Wind Tunnel from Reynolds numbers of 2.4 × 10 5 to 1.0 × 10 6 . In addition to transition-free measurements, potential drag reductions using artificial turbulators were explored, although the benefits were found to be limited for this application. Finally, performance predictions from two well-known computer codes are compared to the data obtained experimentally, and both are found to generate results that are in good agreement with the wind-tunnel measurements. Nomenclature CP pressure coefficient, (pl - p∞ )/q∞ L. lower surface R Reynolds number based on free-stream conditions and airfoil chord S. boundary-layer separation location, xS/c T. boundary-layer transition location, xT/c U. upper surface c airfoil chord cd profile-drag coefficient cl section lift coefficient cm section pitching-moment coefficient about the quarter-chord point p static pressure, Pa (lbf/ft 2