Rotation of a melting ice at the surface of a pool

TL;DR

This study investigates the rotation of large melting ice discs on water surfaces, revealing that vortex-induced flows caused by temperature gradients can induce such rotation, supported by experimental observations and flow visualization.

Contribution

The paper introduces a model experiment demonstrating how vortex flows beneath melting ice discs cause their rotation, highlighting a generic mechanism for floating object rotation.

Findings

Vortex flow beneath ice induces rotation.

Rotation speed increases with bath temperature.

Flow visualization confirms vortex presence.

Abstract

Large circular ice blocks up to 80 m of diameter have been observed on frozen river around the world. This rare event has been reported in a publication in 1993. This fascinating self-fashioned object slowly rotates at about 1$^o$ per second. In this paper, we report a model experiment consisting in a 85 mm of diameter ice disc at the surface of a thermalised pool. The rotation speed has been found to increase with the bath temperature. Using particle image velocimetry technique, we evidence the presence of a vortex below the ice block. This vortex results from the descending flow of high density water at 4$^o$C. The vorticity of the vortex induces the rotation of the ice block. This mechanism is generic of any vertical flow that generates a vortex which induces the rotation of a floating object.