Fluctuation-Dissipation Relations and statistical temperatures in a turbulent von K\'arm\'an flow

TL;DR

This paper experimentally investigates turbulence in a von Kármán flow, demonstrating that its fluctuations obey Fluctuation-Dissipation Relations and enabling the measurement of observable-dependent statistical temperatures.

Contribution

It introduces the application of Fluctuation-Dissipation Relations to non-homogeneous turbulence and measures statistical temperatures, revealing their dependence on observables.

Findings

Fluctuations satisfy Fluctuation-Dissipation Relations

Statistical temperatures depend on the observable

Experimental characterization of turbulence fluctuations

Abstract

We experimentally characterize the fluctuations of the non-homogeneous non-isotropic turbulence in an axisymmetric von K\'arm\'an flow. We show that these fluctuations satisfy relations analogous to classical Fluctuation-Dissipation Relations (FDRs) in statistical mechanics. We use these relations to measure statistical temperatures of turbulence. The values of these temperatures are found to be dependent on the considered observable as already evidenced in other far from equilibrium systems.