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The aim of this research is to study the potential use of adaptive multi-winglets for the reduction of induced drag through variations of winglet cant angles. Different studies have shown that the flow around and over the wing tip can be redirected using small aerodynamic surfaces, thereby reducing the induced drag. The model tested is composed of a rectangular wing using an NACA 65 3 -018 profile with three winglets called 'tip-sails,' which are small wings without sweep along the 25 per cent chord line. The tests were made at a Reynolds number of 350 000. The results are analysed in terms of lift and drag. Results show that it is possible to find the best configuration of the three winglets to obtain the optimum aerodynamic performance for each flow regime in climb and cruise.

A direct optimization study was performed to produce a preliminary evaluation of the potential benefits of a mission adaptive wing employing variable camber technology in typical jet transport aircraft missions, in terms of fuel efficiency increase directly obtainable from airfoil viscous drag reduction alone. A 2-D airfoil analysis approach was adopted, associated with an idealized variable camber mechanism based on elastic deformation and surface extension. Using a direct function optimization program coupled to a viscous-inviscid airfoil analysis routine, optimized variable camber configurations were obtained for several weight conditions of a typical transport aircraft along a sub-critical cruise mission leg. Independent runs were executed considering only trailing and both leading and trailing-edge camber variation and, for each of them, an integrated range parameter has been obtained, proportional to the maximum possible aircraft range. Results indicate that the range increases up to 7.03% over the base airfoil that could be reached with camber variation in the trailing edge region only, and up to 24.6% when leading edge adaptation was considered simultaneously. However, pressure distribution results indicate that the high leading-edge curvatures required for that would probably decrease cruise critical Mach. On other hand, the trailing-edge only approach may offer better conditions for supercritical cruise

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