Identified vortices in the artificial flow of Fig. 9. Top panel: position and the size of nine identified vortices. Green colored vortices rotate counter-clockwise, the pink ones rotate clockwise. The velocity field is displayed by a vector plot. Grid cells labeled as noise are shown in gray. Bottom panels: close-ups on the different vortices. The velocity field is represented by streamlines. Stars denote the center of the vortices and the radii are computed according to Eq. (24).