What Causes Liquid to Form a Link Chain Shape When Poured Slowly?

[johnsmi]

Hi,

I've been away for quite some time but I'm back now.

After some observations lately, I noticed an interesting thing about pouring liquids.
While pouring a liquid out of a bottle (you should try out next time you pour your milk or somthing) the liquid, providing it is poured slowly and at a constant speed forms a link chain shape :

here are some examples: but you should really try it yourself to see:

http://fotosa.ru/stock_photo/Creatas_JI/p_432017.jpg

http://www.fotobank.ru/img/FC02-8358.jpg?size=l

Does anyone have an idea why?

Thank you

 

[Dadface]

Nice observation.I suspect that the shape with which the liquid leaves the bottle/container has a large effect.The bottom part of the liquid stream initially leaves the container with a shape determined by the lip of the container and the top part of the stream is more flattened.As it falls surface tension tends to pull the stream into a more cylindrical shape and this possibly may result in oscillations of the stream.Other factors such as viscosity must play a part.These are just my first impression thoughts.

 

[fawk3s]

Could also have something to do with the pressure differences in liquid due to the upper liquid pressing on the liquid beneath it right near the edge of the bottle. Might cause an extra acceleration on one side, and since the other part (upper liquid) is moving slower, the liquid which is going faster could be dragging it along for the ride, giving the whole thing that spin.
Just my humble opinion.

 

[Andy Resnick]

Fluid jets are a venerable problem, and the question of stability has only been solved for axisymmetric cases. Your observation is due, in part, to the fact that fluid is not issuing from an orifice (in the sense that cylindrical jets issue from an orifice). Consequently, your problem is the free surface of the fluid *everywhere*, including the fluid "still in the container".

There's only a few statements that can be made at this time: that the local curvature reflects the (local) pressure jump across the interface, and the interfacial energy acts to minimize the surface area.

I haven't read this:

http://www3.interscience.wiley.com/journal/117943507/abstract?CRETRY=1&SRETRY=0

but it should give you an idea of what is considered state-of-the-art knowledge.