# Does a whirlpool(vortex in water) continue in air(vortex in air),and when does a vortex stop?

First part:
The question is both about the continuity of the water vortex(whirlpool) to vortex in air in time and in space.
About continuity in time,does the vortex of the water slowly produce a vortex in the air because the vortex at the surface of the water(circle) causes frictional forces on the air molecules and thus makes them move in a circle(on the boundary of water-air) and because air is a continuous medium it also creates a vortex?

Second part:
When does a vortex stop?And why(detailed explanation if possible-my knowledge in fluid mechanics go as far as the navier-stokes equations)?

• I can't answer your questions Landos, but do make sure you experiment with Falaco solitons, see arxiv.org/abs/gr-qc/0101098. Jul 18, 2015 at 12:10

First Part.

No. The vortex is caused by some internal forces of the fluid. It can't end inside the fluid. (Helmholtz's theorem) Some rotation can, and will be transferred like in any surface contact, but this will never create any vortex. Theoretically it might be possible if you have some thin layer of less dense fluid above the vortex fluid. But in case of an atmosphere; you won't never reach the other side, and thus you can't form a Vortex. Only small rotation.

Second part.

It's (obviously?) the frictional-like losses. Fully developed Vortex rotates similarily like a solid object. See Rankine Vortex. This means that it doesn't have internal viscous losses. That's why it can rotate so long compared to convenient vorticity. The funny thing is the optical behaviour of a Vortex; at the very point when this developes, it creates this optical change; The optics of vortex (in water): why there is a bright ring? Please look the editions of this question. There is a more pics.

• thank you! Your other question is interesting as well! You should start a bounty with it! Nov 12, 2015 at 22:53