Von Kármán Vortex Street in Turbulent Flow

A von Kármán vortex street (named after the fluid dynamicist Theodore von Kármán) is a phenomenon in fluid dynamics occurring with turbulent flow at a high Reynolds number. It consists typically of a pattern of swirling vortices in alternating directions that are caused, for example, by the unsteady separation of a fluid flowing over a rapidly moving cylinder. An empirical relation proposed by Strouhal gives , where is the vortex shedding frequency, is the diameter of the cylinder, and is the flow velocity. For a fluid with kinematic viscosity , the Reynolds number is generally in the range 100 to to exhibit this behavior. The vortex shedding frequency describes the rate at which vortices are formed in the wake of the moving cylinder. This phenomenon can sometimes cause vibrations near the frequency in wires or antennas subjected to high winds.

This Demonstration is intended to be qualitative and highly schematic. For more realistic photographs and illustrations, see http://en.wikipedia.org/wiki/Karman_vortex_street.