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Levitation by Thin Viscous Layers
The results of experimental investigations into balancing cuboids, cylinders and spheres‘ on a vertical moving wall which is covered a thin layer of
viscous fluid are discussed. It is found that balance can be achieved over
a narrow range of speeds in all cases. Systematic results for spheres and
cylinders have been found but interpretation of them in terms of lubrica-
tion theory remains a challenge. Good accord is found with predictions
of a lubrication model for cuboids. An essential feature of the flow is the
creation of a tongue of viscous fluid which propagates down the wall.