Thick Supercritical Airfoils with Low Drag and Natural Laminar Flow

A family of natural laminar flow-capable, supercritical airfoils has been designed to have good characteristics with turbulent flow while being capable of supporting up to 70% chord natural laminar flow in favorable conditions. Tests are reported on airfoils of 16 and 21% chord maximum thicknesses in NAE 15x60 in. twodimensional wind tunnel. At Reynolds numbers up to 10 million and over a narrow range of Mach numbers close to their design conditions, the airfoils supported extensive runs of laminar flow and their drag was reduced more than 50% relative to values with turbulent boundary layers. At higher Reynolds numbers, the natural laminar flow capability diminished rapidly due to various factors. The airfoil cruise drag characteristics at all Reynolds numbers tested (8-20 million) were markedly superior to airfoils of similar thickness tested previously in the same facility.