Aerodynamic Design of Wingtip Devices Using Far-field Drag Decomposition

Computational Fluid Dynamics (CFD) has become widely used for civil aircraft. However, the commonly used wall integration method for drag prediction based on Reynolds- averaged Navier-Stokes (RANS) equations still has some shortcomings. Far-field drag decomposition (FDD) method was developed as an alternative to improve the drag prediction accuracy and to provide a powerful analysis tool. FDD is capable of decomposing the drag into viscous, shock, induced, and spurious drag components, which provides invaluable insight into the relationship between drag and flow phenomena. Despite all the strengths, FDD is seldom used for aerodynamic shape design and optimization. In this paper, FDD was used to design wingtip devices for a business aircraft. Five spiroid and one blended winglet were compared with baseline wing and tip-extension configuration. Results indicate that all drag components were quantified successfully and the trade-off between induced drag and other drag components was better explained. The spiroid winglet with new foil gives the lowest total drag and wave drag.