Turbulent zonal winds in the lab: interaction with topography and transport properties
| Quand ? |
Le 27/11/2025, de 11:00 à 12:00 |
|---|---|
| Où ? | MGN1 105 |
| Participants |
Daphné Lemasquerier |
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Zonal jets, coherent east-west currents, are found in various planetary fluid layers, including Earth's oceans, gas giant atmospheres, icy moon oceans, and planetary liquid cores. In many of these systems, zonal jets interact with solid boundaries featuring topography, such as the ocean's bathymetry or the Core-Mantle boundary. Despite their ubiquity, many outstanding questions remain regarding the dynamics of turbulent zonal jets, partly due to the theoretical, numerical, or experimental challenge of modeling the extreme regime in which they emerge.
This talk presents a laboratory model of rapidly-rotating thermal convection, the "Coreaboloid" device at UCLA, where turbulent zonal jets spontaneously emerge. The setup is a 75cm-diameter water tank rotating at speeds up to 72 revolutions per minute. The deflection of the free surface due to the fast rotation provides a strong topographic β-effect, and the flow is forced by differential heating. I will present preliminary results on the interaction between zonal jets and localized topography, particularly the formation of stationary Rossby waves downstream of the topography, which influence the jets' amplitude, number, and position.
Additionally, I will discuss the transport properties of turbulent flow with zonal jets. Synthetic Lagrangian trajectories are computed from time-resolved experimental velocity fields, from which we measure relative (two-particle) dispersion. We identify a Richardson regime above the energy injection scale and a diffusive regime above the scale where turbulence becomes anisotropic due to interactions with Rossby waves. Our analysis of turbulent diffusivity shows good agreement with mixing-length and zonostrophic theories, but suggest a shallower dependence on the energy dissipation rate.