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Morphological Transitions in Partially Gas-Fluidized Granular Mixtures

Anders Nermoen

Mercredi 9 juin 2010

mercredi 9 juin à 11h en salle C. Brot

Experiments were conducted to investigate the patterns growing in the partially fluidized state as large particles sediment out of a fluidized bi-modal sized granular mixture. Partial fluidization occurs when the system is driven at imposed gas velocities insufficient to fluidize all of the constituent particles of the system. A variety of patterns grow dependent on the imposed mixing concentration of large and small particles and the gas velocity. We will show how vertically oriented pipes, containing large particles grow due to a feed back mechanism in which fluidization is localized due to flow localization caused by heterogeneities in the permeability field in de-fluidized zone. The sedimentation of the large particles focus the flow, such that a pattern vertically oriented pipes of large particles develop. We discuss how the interplay between heterogeneities in material properties, fluid flow and fluid induced deformation may be relevant to a variety of geological processes.

Invité par Christophe Raufaste