Wed May 15th 2013
Seminar Physics of the Kugel Fountain
Ko van der Weele


A striking example of levitation is encountered in the "kugel fountain" where a granite sphere, sometimes weighing over a ton, is kept aloft by a thin film of flowing water. In this talk we explain the working principle behind this levitation. We show that the fountain can be viewed as a giant roller bearing and thus forms a prime example of lubrication theory. It is demonstrated how the viscosity and flow rate of the liquid determine (i) the remarkably small thickness of the film supporting the sphere and (ii) the surprisingly long time it takes for rotations to damp out. The theoretical results compare well with measurements on a fountain holding a granite sphere of one meter in diameter. We close by discussing several related cases of levitation by lubrication.
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The 10th Complex Motion in Fluids 2021
Max Planck Gesellschaft
Centre for Scientific Computing