Aerodynamic Evaluation of NACA 6-Series Airfoils for High-Altitude Glider Applications

Abstract

High-altitude gliders face the problems of low Reynolds numbers and reduced air density, resulting in efficient airfoil design being critical. This study compared the NACA 63-618 and 64-618 airfoil at a Re = 2 x 10 6  through the use of XFOIL, while turbulence is modeled by adjusting the Ncrit values from 3-16. While both airfoils displayed similar lift results, the drag and efficiency were affected by the surface smoothness. The 63-618 had higher lift-to-drag ratios in smoother conditions, while the 64-618 was more stable in moderate turbulence. For both, maximum efficiency occurred at an angle of attack between 2 and 4 degrees. The results also suggested that an Ncrit of 7-8 is best representative for high-altitude performance for glider applications.