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
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.