Vortex pair: a mesmerizing photo

by Yi Zhang

Physics Today has this beautiful and mesmerizing photo of vortex pair visualized by laser-induced fluorescence. The description of the photo:

Reproducing the phenomenon at the laboratory scale, Charles Williamson and coworkers at Cornell University have developed a novel laser-induced fluorescence technique for visualizing how vortex pairs interact with the ground. They pool dye on a horizontal surface prior to launching the primary vortices from rotating flaps above it, and then illuminate the system with a laser light sheet. In this image, green dye visualizes the secondary vortices, which have been generated by the ground interaction and swept up above the red primary vortices. The vortex pairs are about 8 cm apart. The lower half of the photo shows the vortex system optically reflected in the surface below.

Charles Williamson’s review of VIV was actually my entry portal to the subject.