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Dense suspensions and equivalent granular packings - Virgile Thiévenaz

Department of Mechanical Engineering, University of California, Santa Barbara


The viscosity of a suspension is known to diverge when the suspension becomes too dense, that is when the particle volume fraction approaches the jamming fraction. Most models used too describe this divergence are partly or fully empirical, and treat the jamming fraction as an adjustable parameter. We introduce a novel physical interpretation of the jamming fraction as the range of motion of particles. This range of motion can be computed by considering an equivalent granular packing. First, this approach provides us with a scaling law for the viscosity, which fits well the experimental measurements at low shear rate. Second, it helps understand why confined suspensions exhibit a higher viscosity. Finally, it enables to compute the viscosity of polydisperse suspensions by considering the jamming fraction of polydisperse granular packings.

In a second part, we investigate the detachment of suspension drops, first monodisperse, then bidisperse. Through scaling arguments, we show that the pinch-off accelerates through a dislocation mechanism, in which the particles move away from each other. The threshold to this regime is set by the suspension viscosity. Using our model for the viscosity, we are able to caracterise the detachment for a suspension of monodisperse or bidisperse particles.

Agenda

séminaire

  • Vendredi 10 septembre 11:00-12:00 - Virgile Thiévenaz

    - Virgile Thiévenaz

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