Energy Loss from Reconnection with a Vortex Mesh

TL;DR

This study uses computational simulations to show that vortex reconnections with a wall-mounted vortex mesh significantly increase energy dissipation in superfluid helium, primarily via Kelvin wave-induced mechanisms.

Contribution

It introduces a new mechanism for energy loss in superfluid vortices involving reconnections with a vortex mesh, highlighting Kelvin wave effects.

Findings

Reconnections can enhance energy loss by up to 100 times.

Kelvin waves generated by reconnections influence vortex dynamics.

Different mechanisms dominate at high and low temperatures.

Abstract

Experiments in superfluid 4He show that at low temperatures, energy dissipation from moving vortices is many orders of magnitude larger than expected from mutual friction. Here we investigate other mechanisms for energy loss by a computational study of a vortex that moves through and reconnects with a mesh of small vortices pinned to the container wall. We find that such reconnections enhance energy loss from the moving vortex by a factor of up to 100 beyond that with no mesh. The enhancement occurs through two different mechanisms, both involving the Kelvin oscillations generated along the vortex by the reconnections. At relatively high temperatures the Kelvin waves increase the vortex motion, leading to more energy loss through mutual friction. As the temperature decreases, the vortex oscillations generate additional reconnection events between the moving vortex and the wall, which decrease the energy of the moving vortex by transfering portions of its length to the pinned mesh on the wall.