Dynamics of wingtip vortex near solid surface

This work presents experimental investigations of the dynamics of a wingtip vortex approaching a solid surface. Wind tunnel experiments were conducted using NACA 0012 wing model at varied distance between the model and the wind tunnel floor. Tests were carried out at 5 and 15 m/s and at an angle of attack of 7.5 degrees. Phase-locked 2D PIV measurements of velocity field were conducted at 5 streamwise locations, three distances between the wing and the wind tunnel floor. The vortex was visualized with vorticity plots to present and report the ground effect. When advecting downstream from the highest position of the wing relative to the floor, the vortex moves inboard. When the distance to the floor decreases, the vortex moves outboard and downward. It results in a smaller core radius and circulation. The study indicates that the ground effect has a significant influence on the vortex wandering at the speed of 5 m/s. At the highest position of the wing off the floor, the vortex centers are more scattered indicating vortex instabilities. Scatter and amplitude of vortex sinusoidal wandering decrease significantly as the distance from the wing to the floor decreases. It was found also that the angle of the plane containing oscillating vortex decreases with the wing-floor distance decrease. At the lowest position of the wing, this plane is almost horizontal.