- #1
oldman
- 632
- 5
I often watch tongues of cold mist spreading over a high plain ahead of an approaching cold front. Their upper surfaces are characteristically corrugated by whorls of mist rotating about a horizontal axis, which form and dissolve as a slab of cold air slides under the warmer upper air. Meshed with corresponding tranparent whorls that (presumably also) form on the lower surface of the upper warm air, I conclude that these rotating structures act as rollers that facilitate the localised shearing of the upper air mass relative to the intruding lower mass. The generation of such horizontal-axed structures shows clearly how easily fluid shear promotes vortex formation.
And in astrophysics, gravitational condensation promotes fluid shear:
The genesis of astronomical objects (for example the outer solar system of planets, moons etc.) is thought to initially involve the gravitational condensation of a rotating fluid mass. Non-interacting particles of the fluid follow Keplerian orbits and such a fluid mass is therefore sheared if it rotates. For example in the case of circular particle orbits in the rotating solar disc the tangential orbital speed varies inversely as the square root of orbit radius, rather than as the radius -- as it would in a non-sheared rigid disc.
One should therefore expect vortices in any rotating, condensing fluid. Indeed vortices in the solar system were proposed as long ago as 1643, by Descartes. And the way vortices can enable gravitational condensation in the solar system has been discussed quite recently by Chavanis.
What is the role of ...compactifying gravity, that leads to localised rotation, that leads to shearing in fluids, that leads to vortices... that are localised rotating fluid masses... that aid compactifying gravity... and so on in a astrophysical and cyclic way?
My head spins whenever I see mist rolling in and then turn to thinking of how the astronomical universe came to be so heterogeneous ? Does anyone know of a good web-accessible review article that can explain the spinning, as it were?
And in astrophysics, gravitational condensation promotes fluid shear:
The genesis of astronomical objects (for example the outer solar system of planets, moons etc.) is thought to initially involve the gravitational condensation of a rotating fluid mass. Non-interacting particles of the fluid follow Keplerian orbits and such a fluid mass is therefore sheared if it rotates. For example in the case of circular particle orbits in the rotating solar disc the tangential orbital speed varies inversely as the square root of orbit radius, rather than as the radius -- as it would in a non-sheared rigid disc.
One should therefore expect vortices in any rotating, condensing fluid. Indeed vortices in the solar system were proposed as long ago as 1643, by Descartes. And the way vortices can enable gravitational condensation in the solar system has been discussed quite recently by Chavanis.
What is the role of ...compactifying gravity, that leads to localised rotation, that leads to shearing in fluids, that leads to vortices... that are localised rotating fluid masses... that aid compactifying gravity... and so on in a astrophysical and cyclic way?
My head spins whenever I see mist rolling in and then turn to thinking of how the astronomical universe came to be so heterogeneous ? Does anyone know of a good web-accessible review article that can explain the spinning, as it were?
