# Detection of vortex coherent structures in superfluid turbulence

## TL;DR

This study compares vortex structures in classical and superfluid turbulence, finding similar statistical properties despite differences in internal structure, indicating negligible impact on macroscopic dynamics.

## Contribution

It provides the first experimental comparison of vortex coherent structures in classical and superfluid turbulence across varying superfluid fractions.

## Key findings

- Vortex filament statistics are similar in classical and superfluid flows.
- The internal structure of vortex filaments has minimal effect on their macroscopic behavior.
- Superfluid vortex bundles behave similarly to classical vortex filaments in turbulence.

## Abstract

Filamentary regions of high vorticity irregularly form and disappear in the turbulent flows of classical fluids. We report an experimental comparative study of these so-called " coherent structures " in a classical versus quantum fluid, using liquid helium with a superfluid fraction varied from 0% up to 83%. The low pressure core of the vorticity filaments is detected by pressure probes located on the sidewall of a 78-cm-diameter Von K\'arm\'an cell driven up to record turbulent intensity (R $\lambda$ $\sim$ $\sqrt$ Re 10000). The statistics of occurrence, magnitude and relative distribution of the filaments in a classical fluid are found indistinguishable from their superfluid counterpart, namely the bundles of quantized vortex lines. This suggest that the internal structure of vortex filaments, as well as their dissipative properties have a negligible impact on their macroscopic dynamics, such as lifetime and intermittent properties.