Vortex-density fluctuations, energy spectra and vortical regions in superfluid turbulence

TL;DR

This paper uses a numerical model to distinguish between different vortex structures in superfluid turbulence, explaining how they contribute separately to the energy spectrum and vortex-density fluctuations.

Contribution

It introduces a decomposition method of vortex line density into coherent bundles and random vortices, clarifying their distinct roles in turbulence spectra.

Findings

Coherent vortex bundles produce the Kolmogorov energy spectrum.

Random vortices account for vortex-density fluctuation spectrum.

The model resolves apparent contradictions in superfluid turbulence measurements.

Abstract

Measurements of the energy spectrum and of the vortex-density fluctuation spectrum in superfluid turbulence seem to contradict each other. Using a numerical model, we show that at each instance of time the total vortex line density can be decomposed into two parts: one formed by metastable bundles of coherent vortices, and one in which the vortices are randomly oriented. We show that the former is responsible for the observed Kolmogorov energy spectrum, and the latter for the spectrum of the vortex line density fluctuations.