Problems with Leading-Edge Flow Control Experiments

Abstract

T HE leading-edge high-lift system on a typical transport aircraft wing typically contributes 2–3% to the overall wing weight. There is therefore considerable incentive to explore leading-edge flow control solutions that could approach the performance of mechanical leading-edge devices but at considerably reduced weight. Indeed, the application of flow control devices at the leading edge has been reported from various sources claiming enhancement in low-speed performance in terms of increased CL and reduced CD [1–5]. However, the technical issue of whether flow control works at the leading edge should be replaced by the technological issue of whether flow control works realistically and successfully at flight Reynolds number conditions. The aim of this Note is to act as a guide for future leading-edge flow control activities conducted in wind tunnels operating at low to medium Reynolds numbers (Re < 10 10) and is specifically applied to civil transport aircraft. The objectives are as follows: 1) Provide a review of relevant literature. 2) Identify airfoil geometric parameters relevant to designing leading-edge flow control experiments. 3) Discuss the effect of Reynolds number on the validity of leading-edge flow control experiments. 4) Describe a wind-tunnel experiment that highlights many of the problems associated with subscale testing of leading-edge flow control.