Séminaire ISTerre

Modal acoustic velocimetry in a gas-filled rotating spheroid

mardi 4 février 2020 - 10h00
Sylvie SU - ISTerre (soutenance de Thèse)
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Zonal flows are expected to play a major role in the heat transfer mechanism of geophysical bodies such as the Earth’s core or Jupiter’s atmosphere. However due to the turbulent regime the systems are in, and the specific force balance, dominated by rotation, it is very hard to accurately model zonal flows. This causes their formation and dynamics to still not be well understood. Experimental studies propose a complementary approach where all scales of structures coexist. However most of the existing experimental set-ups remain far from the relevant regimes found in the natural systems. We present a new laboratory experiment built to study zonal flows induced by thermal convection, called ZoRo. The originality of this new apparatus resides in the fact that the balances, forcings and geometry are closest to the geophysical bodies. In order to match those, ZoRo is a rapidly rotating spheroid (flattened sphere) filled with air. Since the working fluid is air (a gas), it is very challenging to accurately measure its velocity. To tackle to this problem, we implemented a new non-intrusive velocimetry technique based on acoustic resonances of the fluid cavity, the modal acoustic velocimetry (MAV). The quantity of interest is velocity, but other effects can influence the acoustic spectrum. In order to isolate its effect, we develop theoretical predictions that take into account the main relevant effects that influence the acoustic spectrum (cavity’s geometry, fluid’s diffusions, container elasticity, etc.). Once the velocity contribution is isolated, it is possible to retrieve the flow field using acoustic frequencies through an inverse problem. We test this method against both synthetic cases and real experimental flows measured in ZoRo. MAV is a well-suited technique for measuring global azimuthal flows such as zonal flows. It is very sensitive to variations in the flow structure, down to a few centimetres. We were able to image the internal flow velocity with non-intrusive sensors thanks to MAV. This thesis is a first landmark towards realistic zonal flows laboratory experiments. The velocimetry technique is fully developed, allowing accurate non-intrusive measurements of zonal flows.

Equipe organisatrice : Géodynamo

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

“Minimalist seismology”: studying earthquakes with sparse instrumentation

jeudi 17 septembre 2026 - 11h00

Mathieu Causse - ISTerre

Equipe organisatrice : Organisation labo

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

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Stable‑to‑dynamic expansion of fault slipping area through fluid injection observed in laboratory experiments using a sub‑meter scale specimen

vendredi 18 septembre 2026 - 14h00

Takatoshi Ito  - Université de Tohoku, Japan

Equipe organisatrice : Mécanique des failles

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

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Tectonics, Mantle Dynamics and Coupled Lithosphere-Mantle-Core Evolution of Earth and Other Rocky Worlds

jeudi 24 septembre 2026 - 11h00

Paul Tackley - ETH Zurich

Equipe organisatrice : Grands Séminaires ISTerre

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

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Tectonics, Mantle Dynamics and Coupled Lithosphere-Mantle-Core Evolution of Earth and Other Rocky Worlds

jeudi 24 septembre 2026 - 11h00

Paul Tackley - ETH Zurich

Equipe organisatrice : Grands Séminaires ISTerre

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

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Apport des expériences analogiques pour la modélisation et le suivi en temps réel de la propagation du magma en profondeur : Exemple du Rift Est Africain

jeudi 1er octobre 2026 - 11h00

Virginie Pinel - ISTerre

Equipe organisatrice : Organisation labo

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

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A t-on encore besoin de plaques pour expliquer la tectonique de la vallée du Rhône et des Alpes Occidentales ?

vendredi 2 octobre 2026 - 11h00

philippe VERNANT - Geosciences Montpellier

Equipe organisatrice : Tectonique active et sismicité

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 2 octobre 2026 - 14h00

Hugo Boulze - 

Equipe organisatrice : Cycle sismique et déformations transitoires

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

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TBA

vendredi 9 octobre 2026 - 11h00

Eric Beaucé - ISTerre

Equipe organisatrice : Cycle sismique et déformations transitoires

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 20 novembre 2026 - 11h00

Farzaneh Mohammadi - ENS Paris

Equipe organisatrice : Cycle sismique et déformations transitoires

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

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