A note on the propagation of quantized vortex rings through a quantum turbulence tangle: Energy transport or energy dissipation?

TL;DR

This study explores how quantized vortex rings behave in quantum turbulence, assessing their role in energy transport and dissipation through simulations and theoretical analysis.

Contribution

It provides new insights into vortex ring dynamics, reconnection effects, and their implications for energy dissipation mechanisms in quantum turbulence.

Findings

Approximately 75% of vortex ring energy is preserved after reconnection.

Ring emission may contribute to energy dissipation in low-density tangles.

At higher densities, vortex rings are unlikely to significantly dissipate energy, favoring the Kelvin wave cascade mechanism.

Abstract

We investigate quantum vortex ring dynamics at scales smaller than the inter-vortex spacing in quantum turbulence. Through geometrical arguments and high resolution numerical simulations we examine the validity of simple estimates of the mean free path and the structure of vortex rings post-reconnection. We find that a large proportion of vortex rings remain coherent objects where approximately $75\%$ of their energy is preserved. This leads us to consider the effectiveness of energy transport in turbulent tangles. Moreover, we show that in low density tangles, appropriate for the ultra-quantum regime, ring emission cannot be ruled out as an important mechanism for energy dissipation. However at higher vortex line densities, typically associated with the quasi-classical regime, loop emission is expected to make a negligible contribution to energy dissipation, even allowing for the fact that our work shows rings can survive multiple reconnection events. Hence the Kelvin wave cascade seems the most plausible mechanism leading to energy dissipation.