Laminar flow

[michel123456]

Fascinating and counterintuitive. Just wanted to share.

 

[imatfaal]

Nice one . Spent first half thinking "so what .. boring" - but then... brilliant demo.

[pears]

Is there not some kind of trickery going on there?

[swansont]

Is there not some kind of trickery going on there?

No, just laminar flow in a viscous medium.

[pears]

For me it's one of those "any sufficiently advanced technology is indistinguishable from magic" moments.

[CaptainPanic]

You should know that what happens in that movie is not 'mixing'. For mixing, you need turbulence (little vortices), and the movie shows (nearly) perfect laminar flow. They use a liquid with a high viscosity: it is easier to avoid turbulence in such a liquid.

 

Laminar flow is comparable to what happens if you take a phone book, and bend it. The pages will slide over each other a bit. Bend it back, and all the pages will end up exactly how they started.

[edit] Or, you could choose to keep bending it further. Whatever you do, page 9 will always come after 8. The fact that the pages don't mix is laminar flow. Turbulence is the equivalent of shredding the book, and tossing it all up into the air.

[Wilmot McCutchen]

What would be the right name for this -- unmixing ... antidiffusion? Momentum is diffused from the slowly rotating cylinder for five revolutions, and then the direction is reversed until the viscous fluid snaps back to its original state of three inclusions at approximately the same depth in the corn syrup. Viscosity is energy storage.

[CharonY]

Both terms would be wrong. The reason being that there is no mixing going, as CaptainPanic aptly described. Diffusion is going on, but it is so slow that it has no impact. Again, as mentioned earlier, due to the high viscosity you get laminar flow (i.e. parallel layers with no turbulence). Alternatively you could scale the system down into very small dimensions and you get the same effect without increasing viscosity.