Helmholt's Theorems
Helmholtz developed these theorems to describe inviscid flows not
always accurate, but a very good model for what we see in vortecies.
We can see that the theorems listed here can be applied to:
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Starting Vortecies
Wingtip Vortex
Helmholtz's first theorem:
The strength of a vortex filament is constant along its length.
Helmholtz's second theorem:
A vortex filament cannot end in a fluid; it must extend to the boundaries of the fluid or form a closed path.
Helmholtz's third theorem:
In the absence of rotational external forces, a fluid that is initially irrotational remains irrotational.