An experimental effort was undertaken to assess the effectiveness and efficiency of three winglets mounted chordwise to the tip of a rectangular wing (NACA 0018 section). The winglets, with an aspect ratio of 3.6, were mounted on a half-span wing having an aspect ratio of 3.1. Twenty configurations of varying dihedral arrangements were analyzed with a vortex lattice method and tested in a low-speed wind tunnel at a Reynolds number of 600,000. In general, the arrangements involving high dihedral angles had lower performance increments, due to lower lift and higher interference drag. More specifically, the results showed that the winglets placed at 60, 45, and 30 degrees, respectively, produced nominal 4% higher lift and 46% lower drag. The most dramatic findings from this study show that positioning the winglet dihedral angles had the result of adjusting the point of maximum L/D and the magnitude of the pitching moment coefficient. These observations suggest that multiple winglet dihedral changes affect the lift, drag, and pitching moment in such a way that they are feasible for use as actively-controlled surfaces to improve the performance of aircraft at various flight conditions and to “tune” the longitudinal stability characteristics of the wing.

This content is only available via PDF.
You do not currently have access to this content.