Etude en laboratoire d'un courant de gravité turbulent sur un talus continental

Abstract : This study characterizes the dynamics of a turbulent gravity current flowing down a uniform slope in a rotating media. These dense overflows are of particular interest in oceanography since it is an important mechanism in renewing deep water as part of the global thermohaline convective cycle. The large Coriolis turntable (LEGI) is used to study at the laboratory scale, a gravity current in similarity with the oceanic scales.
The propagation of such currents is strongly influenced by rotation, bottom topography and mixing with the ambient fluid, that induce unstable dynamics. Interactions between the gravity current and the ambient fluid, due to entrainment and detrainment phenomena, control the stabilization depth of the main current along the coast, as well as its velocity and density.
Scaling laws are derived, describing the main properties of the flow along the slope, where the buoyancy flux is conserved.
This highly turbulent regime leads to a self-similar behaviour of the flow.
Analysis of experimental results allowed to check these scaling laws and to study the turbulent structure of the flow.
Large scale instabilities are observed, generating cyclonic vortices also visible in oceanic flows. The sudy of their characteristics suggests the mechanism of their formation. A qualitative comparison of experimental results was made with in-situ measurements in the Denmark Strait Overflow.
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  • HAL Id : tel-00011713, version 1

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Sabine Décamp. Etude en laboratoire d'un courant de gravité turbulent sur un talus continental. Océan, Atmosphère. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00011713⟩

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