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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 ...

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Good question. My Problem is that I can't give you a "Mainstream answer". The reason is that Turbulence is considered happening In three space dimensions and time, given an initial velocity field, there exists a vector velocity and a scalar pressure field, which are both smooth and globally defined, that solve the Navier–Stokes equations. But with these ...

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On the scale of galactic spiral arms, the central black hole is gravitationally utterly insignificant. I'll illustrate with an example, NGC 524. Of spiral galaxies (this is technically an S0, but there's still spiral structure) with measured black hole masses, NGC 524 has one of the most massive. Here's a picture of the galaxy: The visible disk has a ...

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$\vec{v}=\vec{w}\times \vec{r}$ $\nabla \times \vec{v}=\nabla \times (\vec{w}\times \vec{r})$ $=\vec{w}(\nabla .\vec{r})-(\vec{w}.\nabla)\vec{r}$ $\nabla .\vec{r} = 3$ and $(\vec{w}.\nabla)\vec{r}=w.(\nabla\vec{r})=w$ therefore $\nabla \times \vec{v}=2w$ or see: \nabla \times \left( {\matrix{ {\widehat i} & {\widehat j} & {\widehat k} ...

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In practice, yes, but you wouldn't even need that: the simple fact that an obstacle pass through the air makes it push apart in front then sucked together on the rear, causing motion on the sides. But such viscous flow displacement would exist only close to the object, while wakes can be very long (see for instance behind cars, when there is some smoke or ...

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