Fluctuations of entropy production in turbulent thermal convection

TL;DR

This study uses numerical simulations to analyze entropy production fluctuations in turbulent thermal convection, revealing large, often negative fluctuations that satisfy fluctuation relations despite system irreversibility.

Contribution

It demonstrates that entropy production fluctuations in turbulent convection follow fluctuation relations, even with time-irreversible dynamics, providing insight into non-equilibrium thermodynamics.

Findings

Entropy production exhibits large fluctuations, including negative values.

Fluctuation relations are verified in turbulent thermal convection.

Entropy production fluctuations are consistent with theoretical predictions.

Abstract

We report on a numerical experiment performed to analyze fluctuations of the entropy production in turbulent thermal convection, a physical configuration that represents here a prototypical case of an out-of-equilibrium dissipative system. We estimate the entropy production from instantaneous measurements of the local temperature and velocity fields sampled along the trajectory of a large number of point-wise Lagrangian tracers. The entropy production is characterized by large fluctuations and becomes often negative. This represents a sort of "finite-time" violation of the second principle of thermodynamics, since the direction of the energy flux is opposite to that prescribed by the external gradient. We clearly show that the fluctuations of entropy production observed in the present system verify the fluctuation relation (FR), even though the system is time-irreversible.