YouTube: Laminar Flow, courtesy UNM.
Comments:
So it’s the thickness of the fluid that makes for the shearing effect? The ‘rewind’ was just mindbogglingly cool.
Thanks for the explanation.
Posted by Garret P Vreeland on 01/31/12 at 09:38 PM
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Ok, so what’s going on there is that laminar flow is linear, not chaotic. And by using a thick fluid, slow motion, and a tricky design for the chamber, they get laminar flow between the two cylinders. The fluid just shears, it doesn’t mix, so it behaves almost like a solid.
At the outer wall is stationary, and at that boundary, there’s no fluid motion. The inner wall moves, but there’s no _relative_ fluid motion (vs. the wall) there either. But there is absolute motion, since the wall has moved. Because it’s laminar flow, each cylindrical ‘layer’ of fluid moves a bit more or less than the ones next to it.
If there was any turbulence, it would mix and be irreversible. But they do it slowly enough that they don’t get turbulence, and can run it backwards.