Physics of chocolate fountain explained

The falling 'curtain' of chocolate in a chocolate fountain surprisingly pulls inwards rather than going straight downwards because of surface tension, researchers have found.
Researchers solved the conundrum of the converging curtain by looking at some classic work on 'water bells'.
"You can build a water bell really easily in your kitchen. Just fix a pen vertically under a tap with a coin flat on top and you will see a beautiful bell-shaped fountain of water," said Helen Wilson, from the University College London (UCL).
The physics of the water bell is exactly the same as the falling curtain of chocolate; and the reason the chocolate falls inwards turns out to be primarily surface tension.

The researchers at UCL also looked at the flow up the pipe to the top of the fountain, and the flow over the plastic tiers that form the distinctive chocolate fountain shape.
"Chocolate fountains are just cool, aren't they!" said Adam Townsend, an author on the research paper published in the European Journal of Physics.
"But it is also nice that they are models of some very important aspects of fluid dynamics," said Townsend.
"Both the chocolate fountain and water bell experiments are surprisingly simple to perform. However they allow us to demonstrate several aspects of fluid dynamics, both Newtonian and non-Newtonian," Wilson added.