Séminaire ISTerre

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On the effects of topography in rapidly rotating fluids: Experiments on the spin-up of a fluid in a straight cylinder with bottom topography

jeudi 28 mars 2024 - 11h00

Jérôme Noir - ETH Zürich, Institut für Geophysik
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Deep seated planetary fluid envelops, such as metallic cores or subsurface oceans, play a fundamental role in the orbital evolution of the celestial objects via transfer of angular momentum and energy dissipation, and the generation of a magnetic field or mixing of chemical species. From a dynamical stand point these buried fluid envelops are rapidly rotating, stably, neutrally or unstably stratified regions enclosed in a solid shell. The interest in their dynamics dates back from the end of the 19th century when scientists proposed to probe internal structures of planets and moons by monitoring their rotation, initiating research on how the presence of fluid layers can reflect in their rotational dynamics. They first considered the hydrodynamics of rapidly rotating spherical shells, then spheroidal shells and more recently tri-axial ellipsoids. Meanwhile, we have geodynamical arguments and seismic observations suggesting that the Earth's Core-Mantle boundary (CMB) may not be a smooth surface but exhibit topographic features of various height and wavelengths, which have not been considered so far.
In this presentation, I will briefly introduce the geophysical context and explain why the abundant results on the topic in oceanography and atmospheric sciences may not apply to those deep fluid layers. I will then present the results from a dedicated experimental study of the Spinup of a rapidly rotating fluid in a straight cylinder with chessboard-like topography at the bottom as a proxy to address topography driven energy dissipation. I will show the particular role played by inertial waves to radiate the energy away from the topography, and shape the internal flows. I will conclude by presenting ongoing and futur theoretical, numerical and experimental investigations to gain further insights.

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Equipe organisatrice : Géodynamo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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