1 Rotary motion of fluid about body or point; vortex.
2 Ideal flow around (not past) circular body, with streamlines concentric circles and velocity inversely proportional to radius (body needed to avoid infinite V at centre).
3 Streamline flow around body of any form, defined as integral of component of velocity along closed circuit with respect to distance travelled around it. Wing lift created
by * superimposed on rectilinear flow past surface (see bound vortex, Magnus, Zhukovsky).
4 Gross motions of planetary (eg Earth) atmosphere.