Effect of Multiscale Endplates on Wing-Tip Vortex

Abstract

An experimental investigation is conducted to study the effect of multiscale endplates on the wing-tip vortex and wing aerodynamic performance at Reynolds numbers of 215,000 and 244,000 based on the wing mean chord of a NACA 0012 half-span wing. Two groups of endplates are tested. The first group has three different fractal patterns applied along the top edge of the endplate, while the second group has three different two-scale patterns applied to its outboard surface. It is experimentally shown that both geometry modifications produce a weaker and less coherent vortex. Moreover, while a peak in the power spectral density of the fluctuating axial velocity at the vortex core at Strouhal numbers between 3 and 10 is observed for the plain endplates of both groups, it vanishes for the multiscale endplates. This suggests that the multiscale endplates act on the vortex structure, making it less coherent through the production of smaller eddies as evidenced by the velocity spectra. The multiscale endplates also show potential improvements in terms of the wing aerodynamic efficiency, with the maximum being up to 11.1% larger than for the corresponding plain endplate.