ABSOLUTE EQUILIBRIUM DYNAMICS IN 3D TURBULENCE
Jean-Baptiste Gorce
Laboratoire Matière et Systèmes Complexes (MSC), Paris
Turbulent flows are complex non-equilibrium systems, characterized by a wide range of interacting length scales. Experimental and numerical studies of three-dimensional turbulence usually focus on how the largest structures in the flow break down into smaller structures. Yet, many geophysical or astrophysical flows involve spatial scales much larger than those at which energy is injected into the flow. At these very large scales, viscous effects are negligible, which raises the question of whether the large scales of three-dimensional turbulence are governed by non-equilibrium dynamics or instead behave as an isolated system at equilibrium.
To directly probe the large-scale dynamics of three-dimensional turbulence, we introduce a new experimental setup and show that the large scales exhibit dynamics similar to those of an equilibrium system, despite being strongly out of equilibrium. We then quantify the temporal decay of the large-scale motions to understand how turbulent flows relax toward equilibrium. These results provide a new framework to describe turbulent flows using concepts from statistical mechanics.
