Superfluid drain vortex

TL;DR

This paper models superfluid drain vortices in liquid helium using the Gross-Pitaevskii equation, revealing that vortex lines twist and strengthen axial flow, simplifying the complex physics of vortices.

Contribution

It introduces a simplified model of superfluid drain vortices capturing key physics, highlighting vortex line twisting and axial flow enhancement.

Findings

Vortex lines twist and bundle in the superfluid drain vortex.

Twisting of vortex lines strengthens axial flow.

Model captures essential physics of superfluid vortices.

Abstract

Drain vortices are among the most common vortices observed in everyday life, yet their physics is complex due to the competition of vorticity's transport and diffusion, and the presence of viscous layers and a free surface. Recently, it has become possible to study experimentally drain vortices in superfluid liquid helium, a fluid in which the physics is simplified by the absence of viscosity and the quantisation of the circulation. Using the Gross-Pitaevskii equation, we make a simple model of the problem which captures the essential physics ingredients, showing that the superfluid drain vortex consists of a bundle of vortex lines which twist, thus strengthening the axial flow into the drain.