Exploring the physics of chocolate fountains

A UCL mathematics student has found that the falling 'curtain' of chocolate in a chocolate fountain surprisingly pulls inwards rather than going straight downwards because of surface tension. "Chocolate fountains are just cool, aren't they!" said Adam Townsend (UCL Mathematics), lead author of the paper based on his MSci project. "But it's also nice that they're models of some very important aspects of fluid dynamics. We've used some serious maths to solve a fun problemwhy the chocolate 'curtain' on a chocolate fountain always falls inwards." The study, published today in  European Journal of Physics , used classic work on 'water bells' to model the fluid dynamics of the chocolate in the fountain. The physics of the water bell is exactly the same as the falling curtain of chocolate, and by using this model the team discovered that surface tension of the chocolate causes it to fall inwards. "You can build a water bell really easily in your kitchen," said Dr Helen Wilson (UCL Mathematics), co-author of the paper and MSci project. "Just fix a pen vertically under a tap with a 10p coin flat on top and you'll see a beautiful bell-shaped fountain of water." The researchers studied the flow of chocolate up the pipe to the top of the fountain, over the plastic tiers that form the distinctive chocolate fountain shape and down as a curtain.