HOW MANUFACTURING INACCURACIES AFFECT VORTICES IN AN AIRFOIL WAKE

We investigate the statistics of individual vortices found in the wake past airfoil NACA 64-618 (or 643618). We use two realizations of this airfoil: the first one is created by a 3D print of the profile downloaded from public database. By using a 3D scanning technology (GOM Atos), we detect the differences from the design geometry. We prepare a better product, which is closer to the design geometry, but still, it is rather far from ideal case. The flow wake past these two airfoils is measured by using Particle Image Velocimetry (PIV). We find the individual vortices in the instantaneous 2D velocity fields. We compare the statistical distributions of the vortex core radii and distance to nearest other vortex. Probability density function (PDF) of core radius scales as R-1.6 and R-2, while the PDF of distance to nearest vortex does as D-3/4 and D-4 . We compare two different realizations of NACA 64-618 airfoil at Reynolds number 3.1 . 10(4) and zero angle of attack.