Statistics of small scale vortex filaments in turbulence

TL;DR

This paper investigates the statistical properties and lifetimes of small-scale vortex filaments in turbulence using combined Lagrangian and Eulerian measurements, revealing their fractal nature and persistence in turbulent flows.

Contribution

It introduces a novel multi-particle correlation technique to quantitatively estimate vortex-filament lifetimes in turbulence.

Findings

Light particles concentrate in high-vorticity filament regions.

Vortex filaments have long lifetimes, some lasting as long as the integral correlation time.

The method can be applied in experiments tracking bubbles in turbulence.

Abstract

We study the statistical properties of coherent, small-scales, filamentary-like structures in Turbulence. In order to follow in time such complex spatial structures, we integrate Lagrangian and Eulerian measurements by seeding the flow with light particles. We show that light particles preferentially concentrate in small filamentary regions of high persistent vorticity (vortex filaments). We measure the fractal dimension of the attracting set and the probability that two particles do not separate for long time lapses. We fortify the signal-to-noise ratio by exploiting multi-particles correlations on the dynamics of bunches of particles. In doing that, we are able to give a first quantitative estimation of the vortex-filaments life-times, showing the presence of events as long as the integral correlation time. The same technique introduced here could be used in experiments as long as one is capable to track clouds of bubbles in turbulence for a relatively long period of time, at high Reynolds numbers; shading light on the dynamics of small-scale vorticity in realistic turbulent flows.