Design and Characterization of High-Lift Capabilities for Slotted, Natural-Laminar-Flow Airfoils

Abstract

Morphing leading-edge shapes are of great interest for natural-laminar-flow airfoils operating in high lift as they can be designed to delay separation without any steps or gaps in the surface geometry. A computational study was performed to explore leading-edge configurations for a high-lift system featuring the S207, slotted, natural-laminar-flow airfoil, which was designed for commercial transport applications. Morphing technology was applied to mitigate abrupt wing-stall characteristics and further increase maximum lift. As a result, significantly higher lift coefficients were obtained. However, signs of wake bursting (i.e., off-body separation and narrow stall region in lift curves) were observed. The high-lift aft element’s position was optimized in a previous study for the S204, a slotted, natural-laminar-flow airfoil designed for business-jet applications. An optimization of S207’s aft element for high-lift is recommended. A constant-width slot between stowed and deployed positions allowed attached flow to be maintained across the aft element, which proved beneficial when combined with leading-edge morphing technology. The use of morphing technology was observed to produce superior high-lift performance over drooped leading edge, as the latter produced detrimental pressure peaks caused by the sharp curvature of the flap-like drooped leading edge’s upper surface that led to compressible stall.