Spheres rotating along a boundary may roll or slide depending on the pressure build-up

What is it about?

This is a detailed experimental and numerical investigation of the transition between rolling and sliding motion of rotating spheres in cylindrical channels. We carry out detailed numerical simulations to provide an accurate set of resistance coefficients which are critical to determine whether the sphere will roll or slide. The numerical simulations are complemented with experiments on magnetic spheres rotated with a rotating magnetic field in glycerol-filled channels.

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Why is it important?

This article builds up on previous literature to provide a highly accurate set of resistance coefficients of spheres particularly in close proximity to a boundary. It is one of the few studies with both numerical modelling and real-life experiments. The transition from rolling to sliding is clearly demonstrated and reasons explained thoroughly.