Vortex filament

From Glossary of Meteorology

vortex filament

A line along which an infinite vorticity in a fluid motion is concentrated, the surrounding fluid being free of vorticity.

In an autobarotropic frictionless fluid, a vortex line always consists of the same fluid particles; the vortex filament is, thus, a vortex line and is the limiting case of a vortex tube as the cross- sectional area of the tube shrinks to zero.