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Formation of impact craters

Members: Y. Bertho, Ph. Gondret, A. Seguin

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Velocity profiles and role of friction during a silo discharge

Member: Y. Bertho
Collaborations: P. Richard (IPR), F. Ludewig, N. Vandewalle (GRASP)

The role of friction on the discharge of a silo is studied by means of numerical simulations (DEM). Velocity profiles are compared to those obtain experimentally and to existing models (e.g. kinematic model). The discharge law obtained for different friction coefficients between the grains is compared to the one observed for the flow of bubbles in a similar geometry.

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Air/grains interactions in vertical granular flows

Members: Y. Bertho, F. Giorgiutti, J.-P. Hulin
Collaborations: H. Herrmann (IfB), J. Hinch (DAMTP)

Dry granular flows in a vertical pipe are studied experimentally. Three different flow regimes are observed as a function of the grain flow rate: dilute and fast regimes, density waves regimes and intermittent dense flows where the coupling between the air and the grains plays a key part.

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Dynamical Janssen effect: force distributions and influence of humidity

Members: Y. Bertho, F. Giorgiutti, J.-P. Hulin

The apparent mass at the bottom of granular packing inside a vertical tube in relative motion is measured experimentally. We have demonstrated that, during the flow, a dynamical equilibrium is reached in the granular packing. We proved that Janssen's model is valid over a broad range of velocities and is verified even more precisely than in the static case. Moreover, a significant dependence on the relative humidity for the apparent mass has been demonstrated experimentally.

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