Rankine vortex

The Rankine vortex is a type of vortex in a viscous fluid. It is named after its discoverer, William John Macquorn Rankine.

A swirling flow in a viscous fluid can be characterized by a forced vortex in its central core, surrounded by a free vortex. In an inviscid fluid, on the other hand, a swirling flow consists entirely of the free vortex with a singularity at its center point instead of the forced vortex core. The tangential velocity of a Rankine vortex with circulation and radius is