Experimental Results for a Low-Reynolds Number Airfoil in a Low-Turbulence Environment

The PSU 94-097 airfoil was originally designed in the early 1990’s for use on winglets of high-performance sailplanes. This design problem is difficult because this application requires the airfoil to operate over a wide range of Reynolds numbers, from roughly 0.7 × 10⁵ to 1.0 × 10⁶. At that time, over two decades ago, to validate the design tools as well as the design itself, high-quality measurements of section characteristics and pressure distributions were made in the Penn State Low-Speed, Low-Turbulence Wind Tunnel from Reynolds numbers of 2.4 × 10⁵ to 1.0 × 10⁶. In addition to free-transition measurements, potential drag reductions using artificial turbulators were explored, although the benefits were found to be limited for this application. Recently, and the subject of this paper, this model was retested in the same facility at Reynolds numbers down to 1.0 × 10⁵. In addition, as this airfoil has also been successfully employed on model aircraft and UAVs, its performance using a simulated simple flap/aileron was also measured and found to be as expected and desired, that is, comparable with similar flapped-equipped airfoils. Finally, as was the case with the results obtained from the original tests, with the exception of the maximum lift coefficient, theoretical predictions using well-known codes are found to be in good agreement with the wind-tunnel measurements.