Tip vortices generated by a wing in ground effect

Abstract

Tip vortices generated by a cambered, single element wing operating in ground effect were studied using a range of methods including particle image velocimetry (PIV), laser Doppler anemometry (LDA), surface pressures, force balance measurements, and surface flow visualization. The wing was placed suction surface down, leading to down-force and a complex system of trailing vortices evolving in proximity to the ground. The characters of the tip vortex led to changes in the aerodynamic force behaviour in ground effect. The down-force was found affected by the presence of separation on the suction surface and the tip vortices. At larger ground heights, a concentrated tip vortex was produced off the edge of the endplate on the wing through separation, contributing to the down-force enhancement process. The tip vortex induced an upwash on the wing, leading to an effective reduction in the incidence of the wing and hence smaller extents of separation near the wing tip. However, vortex breakdown occurred as the wing was lowered to the ground, leading to a slow down in the force enhancement.