Viscous thread falling on a moving belt

A stream of very viscous syrup falls from a nozzle onto a moving belt. Initially, the belt is moving so fast that the thread is just pulled out straight. As the speed of the belt is reduced, the thread first bifurcates to a meandering state, and then to a "figure eight" state. Finally, the thread falls into a coiling motion similar to what it would do on a non-moving surface.

The syrup is Newtonian.

See http://www.physics.utoronto.ca/nonlin...

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  Science & Technology

[Paul Meynell]

Can anybody explain yet why syrup falls back from a spoon to the Canon in a figure of eight? I saw this question asked on a science program in England 30 years ago and they said nobody knew the answer, has anybody worked it out yet?

[Stephen Morris]

Yes, a great deal about this has been worked out. It is difficult to explain in words, however. Canon?

[khyar]

Wow, that last pattern of behaviour where it forms loops on one side or the other has a resemblance to the 'walkabout' instability of a 2D leapfrogging vortex system (of all things!). Here is my inviscid simulation of such a thing /watch?v=4bhuFFZzJMQ

[Stephen Morris]

I don't think there is a connection. This is totally viscous. Fluid mechanics is just that cool.

[MRtatersryummy]

Can someone explain why this happens?

[Stephen Morris]

Depends on what you mean by "explain". In detail, there is a lot to it. See the papers. In general, the thread has to coil to take up its more and more of its length on the slowing belt.

[keygenex]

привет с ленты

[Stephen Morris]

In this movie, the parameters are changed fast, so there are a lot of transient effects.

To my knowledge, it has not been done carefully with a non-newtonian fluid. This would make a difference.

[Zephyr Morley]

amazing!

[Paul Meynell]

Can

[shinysquid]

so this is what engineers watch for fun... hmmm....

[RandomNES]

how did i get here from Skyrim vids?