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instabilités dans les écoulements granulaires

Abstract : In spite of their importance in many industrials and geophysical processes, granular flows are still not completely understood. In this thesis, we study two instabilities that occur when a granular material is flowing under gravity down a rough inclined plane. We first study a new instability observed for rapid and dilute flows, when the plane is strongly inclined. This instability correspond to the spontaneous formation of longitudinal vortices in the flow. From the experimental measurements, we propose an instability mechanism based on the concept of "granular temperature". This mechanism is then validated by a stability analysis in the framework of the kinetic theory of granular flows. The second instability we have studied appears in the dense flow regime. In a given range of parameters, we observe the formation of long surface waves that propagate downstream. We have precisely studied the formation of these surface waves by forcing the instability, in the spirit of open flows stability experiments in fluid mechanics. The results are then compared with a depth-averaged approach. This study shows that the properties of the "classical" long surface waves instability may be deeply modified by the rheology of dense granular flows.
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Contributor : Yoel Forterre <>
Submitted on : Tuesday, August 30, 2005 - 4:28:43 PM
Last modification on : Thursday, January 18, 2018 - 1:26:50 AM
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Yoel Forterre. instabilités dans les écoulements granulaires. Dynamique des Fluides [physics.flu-dyn]. Université de Provence - Aix-Marseille I, 2002. Français. ⟨tel-00010005⟩

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