think or thwim

Michel Versluis at the University of Twente in the Netherlands filmed pouring liquids with a high speed camera to understand this strange behavior.

From an April 2006 Nature article:

It could happen with everything from tomato ketchup to yoghurt, paints, shampoo and liquid soap, Versluis says.

The reason you have probably never noticed this so-called Kaye effect is that it is generally over in an instant. The whole process, from the emergence of the jet to its merging with the incoming stream, typically takes about 300 milliseconds, says Versluis. “It’s usually so short that you don’t see it with the naked eye.”

Versluis says the effect should happen in any liquid that displays shear-thinning behaviour. This means that as the liquid flows, its viscosity decreases; that is, it gets thinner….

Pouring a column of these viscous liquids on to a surface initially creates a coiled heap. But at some point the stream slides down the side of the heap. A thin layer of shear-thinned liquid acts as a kind of lubricant between the two, preventing them from mixing. The stream may then spring up from a dimple on the surface of the heap, just as an Olympic ski-jumper leaps from the lip of a ramp. The researchers’ video images show a kind of U-shaped stream launching off the surface.

:: Justinsomnia