Investigations of a Wing Tip Vortex in Air by Means of DPIV

Abstract

This paper presents results of Particle Image Velocimetry measurements on the tip vortex of a NACA0012 wing. These results were achieved utilizzing a digital recording technique based on a modified CCD video camera and an evaluation process which is based on the cross correlation technique. Instantaneous velocity fields showing the complete vortex could be gained. Because for each set of experiment parameters a large number of PIV images were recorded, and because the evaluation was fully automatic, time averaging of several hundred images was also possible. Locating the vortex core in each measured velocity field for a fixed free stream velocity allowed to determine the trajectory of the vortex core with respect to the angle of attack. Due to the higher spatial resolution of PIV images taken with a smaller field of view it was also possible to determine the azimuthal velocity components along a line through the vortex core.