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Écoulement de suspensions granulaires modèles

Abstract : We experimentally study the flow of dense granular suspensions. The suspensions are made of mono-disperse, spherical, non-Brownian polystyrene beads immersed in a density matched silicon oil. The volume fraction $\phi$ varies from 30 to 61%. We investigate the flow behaviour of these dense granular suspensions by the use of two complementary model experiments: shear flow on an inclined plane and elongational flow during the detachment of a droplet. We prove that the inclined plane is a useful apparatus to explore the continuous transition from an effective viscous flow (high thickness) to dense "pseudo-granular" flow (low thickness). A mesoscopic length scale is evidenced that separates the two flowing regimes and diverges when $\phi$ approaches the jamming limit. We show that our experimental results are consistent with a fully Newtonian rheology -i.e. without stress threshold- but with an effective viscosity depending on the thickness of the layer. Moreover, we show that particle migration can be neglected. This set-up allows for directly measuring the viscosity up to volume fractions of 61%, which is impossible in a classical rheometer. During "pinch-off" experiments, we prove that the elongational viscosity is identical to the one we measure on a pure viscous fluid. Nevertheless, the final detachment is accelerated by the presence of grains and is independent of the grain concentration, but highly dependent on the grain size.
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Submitted on : Friday, March 12, 2010 - 3:43:25 PM
Last modification on : Friday, August 5, 2022 - 11:54:08 AM
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  • HAL Id : tel-00463534, version 1


Claire Bonnoit. Écoulement de suspensions granulaires modèles. Dynamique des Fluides [physics.flu-dyn]. ESPCI ParisTECH, 2009. Français. ⟨tel-00463534⟩



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