The purpose of this work is to design an aerodynamically shaped vortex generator set-up to delay flow separation on a swept wing with dihedral of an unmanned aerial vehicle being designed at KTH Royal Institute of Technology. Therefore, a 2.5D CFD study of the wing was performed using the Spalart-Allmaras turbulence model. The optimization of the vortex generator set-up followed a multipoint Pareto strategy to establish an optimum design of the vortex generator vanes including its airfoil cross-section. The resulting vortex generator setup achieved a respective improvement of the maximum lift coefficient and stall angle of attack with respect to the baseline wing of 26.34% and 3 deg as a counter-rotating arrangement and 24.02% and 2 deg as a co-rotating set-up. The optimization procedure showed that the optimum cant angle of the vanes, a geometric parameter not tested in the available literature, contributed to 2.45% of the overall improvement of the maximum lift coefficient. The optimization procedure also showed that the flow separation control performance of the vortex generators is sensitive to its airfoil cross-section, and among all the airfoils tested, the S1223 cross-section showed a superior performance. Finally, the optimum height-to-boundary-layer-thickness ratio obtained was 1.301 and a further numerical flow visualization demonstrated that the aerodynamically shaped vortex generators produced a vortex system similar to that of a delta wing, with the difference of the influence of the wing's wall on the axial flow, that generated a primary vortex submerged in the boundary layer. Because of the resulting leading-edge separation vortex system, the penalty drag of the optimized aerodynamically shaped vortex generators was comparable to that of a conventional, flat-plate vortex generator. Nonetheless, the airfoil-shaped vanes produced higher maximum lift coefficients than the flat-plate vanes configurations.
Part of ISBN 978-1-62410-711-5
QC 20250217