Improving the UAS-S4 Éhecal airfoil high angles-of-attack performance characteristics using a morphing wing approach

In this paper, a morphing wing approach with a new methodology and its results for the high angles-of-attack optimization of the S4 unmanned aerial system airfoil are described. The boundary layer separation delay, coupled with an increase of the maximum lift coefficient, was achieved using an in-house optimization tool based on the artificial bee colony algorithm, coupled with the Broyden–Fletcher–Goldfarb–Shanno algorithm to provide a final refinement. The obtained results were validated with an advanced, multi-objective, commercially available optimizing tool. The aerodynamic calculations were performed using a two-dimensional linear panel method, coupled with an incompressible boundary layer model and a transition estimation criterion. For very small displacements of the airfoil surface, of less than 2.5 mm, lift coefficient increases of up to 18% together with relevant drag reductions have been achieved, successfully delaying separation for the high angles-of-attack range.