The Emergence of Small Scales in Vortex Ring Collisions
Vortex
https://en.wikipedia.org/wiki/VortexHalf vortex rings in a pool - Physics Girl
Square vortex ring oscillations - Physics Girl
Mechanism of axis switching in low aspect-ratio rectangular jets
Knotted vortex rings - Physics Girl
Helmholtz's theorems
https://en.wikipedia.org/wiki/Helmholtz%27s_theoremsTwo Vortex Rings Colliding - SmarterEveryDay