From Energy Cascade to Thermalization in 3D Turbulence
| Quand ? |
Le 01/10/2026, de 11:00 à 12:00 |
|---|---|
| Où ? | Amphi F |
| S'adresser à | Benjamin Apffel |
| Participants |
Jean-Baptise Gorce |
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Turbulence is ubiquitous in atmospheric and industrial flows, presenting complex out-of-equilibrium dynamics across interacting length scales. While experiments generally focus on the energy cascade driven by large-scale forcing, natural flows involve spatial scales larger than the forcing itself. At these length scales, viscous effects are negligible, implying that non-dissipative equations govern the flow dynamics. This raises a fundamental question of whether these large scales maintain a traditional out-of-equilibrium behavior, or behave as an isolated statistical equilibrium.
To address this, we present an experimental setup featuring a clear separation between the forcing scale and the system size. We demonstrate that the resulting flow satisfies Kolmogorov theory and provide the first experimental evidence that the large scales of 3D turbulence thermalize into an absolute equilibrium regime. Furthermore, we quantify the temporal decay of turbulence, establishing a direct link between large-scale Saffman invariants and the energy spectrum. These findings provide a new framework to describe turbulent flows using statistical mechanics.