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THE VORTEX

In the case of a vortex, the flow field is purely tangential.

The picture is similar to that of a source but streamlines and
equipotential lines are reversed.

The complex potential is

There is again a singularity at the origin, this time associated to
the fact that the circulation along any closed curve including the
origin is nonzero and equal to . If the
closed curve does not include the origin, the circulation will be zero.