Rotation of a submerged finite cylinder moving down a soft incline

TL;DR

This study investigates the steady spinning and sliding of a submerged finite cylinder on a soft incline, combining experimental measurements with theoretical analysis of elastohydrodynamic and edge effects.

Contribution

It introduces a unified framework linking elastohydrodynamic torque and edge effects to the cylinder's aspect ratio and substrate deformability.

Findings

Spinning is driven by elastohydrodynamic and edge effects.

Transition from edge-effect to gap-dominated regime observed.

Experimental results align with theoretical predictions.

Abstract

A submerged finite cylinder moving under its own weight along a soft incline lifts off and slides at a steady velocity while also spinning. Here, we experimentally quantify the steady spinning of the cylinder and show theoretically that it is due to a combination of an elastohydrodynamic torque generated by flow in the variable gap, and the viscous friction on the edges of the finite-length cylinder. The relative influence of the latter depends on the aspect ratio of the cylinder as well as the deformability of the substrate, which we express in term of a single scaled compliance parameter. By varying this compliance parameter, we show that our experimental results are consistent with a transition from an edge-effect dominated regime for short cylinders to a gap-dominated elastohydrodynamic regime when the cylinder is very long.