Aerodynamic performance improvement of the UAS-S4 Éhecatl morphing airfoil using novel optimization techniques

In this paper, we present a morphing wing concept of the airfoil of the S4 unmanned aerial system, the new optimization methodology and the results obtained for multiple flight conditions. The reduction of the airfoil drag coefficient has been achieved using an in-house optimization tool based on the relatively new Artificial Bee Colony algorithm, coupled with the Broyden–Fletcher–Goldfarb–Shanno algorithm to provide a final refinement of the solution. A broad range of speeds and angles of attack have been studied. An advanced, multi-objective, commercially available optimizing tool was used to validate the proposed optimization strategy and the obtained results. The aerodynamic calculations were performed using the XFOIL solver, a two-dimensional linear panel method, coupled with an incompressible boundary layer model and a transition estimation criterion, to provide accurate estimations of the airfoil drag coefficient. Drag reductions of up to 14% have been achieved for a wide range of different flight conditions, using very small displacements of the airfoil surface, of only 2.5 mm.