I've recently been studying aircraft trailing vortices and have been reading various papers regarding vortices. However, my aerodynamics is very rusty, I've been confused about the vorticity of these vortices. In Fundamentals of Aerodynamics (Anderson), Ch 3, Vortex flow is shown to be irrotational everywhere except when r = 0, which has infinitie voriticity. However, all the vortices that I've come across in various papers have a particular (non-zero) vorticity, eg a Gaussian profile for the Lamb-Oseen vortex. Could someone please help me with this. Cheers.