Supercritical Airfoil Design for Future HALE Concepts

Abstract

This paper presents design and analysis of a new airfoil for future High-Altitude Long-Endurance (HALE) aircraft that has an operational condition at supercritical speeds. The XFOIL and MSES computational codes were used to design, modify and analyze the airfoil. The airfoil has enough thickness and performance to meet the requirements set for one of the AFRL SensorCraft concepts; a joined-wing configuration with diamondshape in planform and front views. This SensorCraft concept’s geometry and operational altitudes and speeds were used to determine the airfoil design conditions. Sensitivity studies were carried out to investigate the effects of Reynolds number and Mach number, along with boundary layer transition parameters. The airfoil has a drag bucket over a large range of lift coefficient. Boundary layer transition location is at about 60% chord upper and 70% chord lower surface, and characterized by a laminar separation bubble, which decreases in size with increases in angle of attack. Further work needs to be performed to validate the design with experiments. NOMENCLATURE AR = Aspect ratio a = freestream speed of sound c = chord CL = airfoil lift coefficient CD = airfoil drag coefficient CM = airfoil moment coefficient CP = surface pressure coefficient L = lift force D = drag force M = freestream Mach number, V/a MD = drag divergence Mach number M = reduced Mach number, L