Design of a Variable Camber Flap for Minimum Drag and Improved Energy Efficiency

Abstract

A variable camber flap concept is optimized to reduce the drag of a low speed light UAV between its stall and cruise speeds using an in-house aerodynamic shape optimization code. The flap, which maintains continuity on the upper surface, was analyzed both numerically and experimentally and was shown to provide important reductions in drag when compared to the clean wing/airfoil in the lower speed range (2.7 % on average for the wing) and to have significant actuation energy savings when compared to a conventional plain flap (in the order of 40%). Although the concept uses current actuator technology and materials it is a good option for improving flight endurance/range at low speed over other more complex and advanced morphing concepts. Nomenclature c = wing/airfoil chord cf = flap chord Cl = airfoil lift coefficient Clmax = maximum airfoil lift coefficient CPa = actuator power coefficient