Large-scale normal fluid circulation in helium superflows

TL;DR

This study uses numerical simulations to reveal that pure helium II superflows involve large-scale normal fluid circulation, matching experimental vortex-line densities and detectable via particle-tracking methods.

Contribution

It introduces a fully-coupled simulation model accounting for vortex back-reaction and boundaries, providing new insights into superflow dynamics.

Findings

Reproduces experimentally measured vortex-line density

Identifies large-scale normal fluid circulation in superflows

Suggests detectability via particle-tracking visualization

Abstract

We perform fully-coupled numerical simulations of helium II pure superflows in a channel, with vortex- line density typical of experiments. Peculiar to our model is the computation of the back-reaction of the superfluid vortex motion on the normal fluid and the presence of solid boundaries. We recover the uniform vortex-line density experimentally measured employing second sound resonators and we show that pure superflow in helium II is associated with a large-scale circulation of the normal fluid which can be detected using existing particle-tracking visualization techniques.