Energy Loss from a Moving Vortex in Superfluid Helium

TL;DR

This study investigates how vortices in superfluid helium lose energy and become pinned on surfaces, revealing different underlying mechanisms influenced by surface and fluid parameters.

Contribution

It provides experimental insights into the distinct mechanisms of energy loss and pinning of vortices, highlighting the role of microscopic vortex reconnections and local fluid velocity.

Findings

Energy loss varies with surface and fluid parameters.

Pinning is primarily influenced by local fluid velocity.

Different mechanisms govern energy loss and pinning.

Abstract

We present measurements on both energy loss and pinning for a vortex terminating on the curved surface of a cylindrical container. We vary surface roughness, cell diameter, fluid velocity, and temperature. Although energy loss and pinning both arise from interactions between the vortex and the surface, their dependences on the experimental parameters differ, suggesting that different mechanisms govern the two effects. We propose that the energy loss stems from reconnections with a mesh of microscopic vortices that covers the cell wall, while pinning is dominated by other influences such as the local fluid velocity.