Laboratory experiments on eddy collisions with multiple islands

We performed laboratory experiments to investigate the interaction between a self-propagating barotropic cyclonic eddy with two vertical cylinders and determine the conditions for an eddy to bifurcate into two or more eddies. As in a previous study, fluid peeled off the edge of the vortex and a "streamer" went counterclockwise around the cylinder. For certain conditions, this fluid formed a new cyclone in the wake of the cylinder. In some cases, two "streamers" formed and went around the two obstacles, each forming a new cyclone. Three parameters were varied: G, the obstacle separation, d, the diameter of the incident vortex and Y, the distance of the center of the vortex from an axis passing through the center of the gap between the obstacles. The number of eddies generated by the interaction depends on the ratio G/d and on the geometry of the encounter, which is given by the ratio Y/g, where g=G/2. Furthermore, in some experiments we observed the formation of an eddy of opposite sign (anticyclonic) downstream of the two obstacles. This is in agreement with recent observations of North Brazil Current Rings, suggesting that these very idealized laboratory experiments may bring some insight to the fate of mesoscale eddies in the ocean.