Probing small-scale intermittency with a fluctuation theorem

TL;DR

This paper applies fluctuation theorems from stochastic thermodynamics to turbulence data, revealing how small-scale intermittency influences entropy production and can be observed at macroscopic scales.

Contribution

It introduces an integral fluctuation theorem for velocity increments in turbulence, linking small-scale intermittency to measurable entropy fluctuations.

Findings

Fluctuation theorems are observable in turbulence data.

Small-scale intermittency generates entropy-consuming trajectories.

The theorem's accuracy depends on tail behavior of velocity distributions.

Abstract

We characterize statistical properties of the flow field in developed turbulence using concepts from stochastic thermodynamics. On the basis of data from a free air-jet experiment, we demonstrate how the dynamic fluctuations induced by small-scale intermittency generate analogs of entropy-consuming trajectories with sufficient weight to make fluctuation theorems observable at the macroscopic scale. We propose an integral fluctuation theorem for the entropy production associated with the stochastic evolution of velocity increments along the eddy-hierarchy and demonstrate its extreme sensitivity to the accurate description of the tails of the velocity distributions.