Shearing of Granular Materials
Brian Utter
Granular flows are ubiquitous in nature and in industry, including processes
such as avalanches, draining of silos, and mixing of pharmaceutical powders.
They are also relatively simple in that you can describe the system after
an intro physics class (e.g. collisions, friction, and kinetic and potential
energy). Despite this, we still don't have an accurate statistical
description of granular systems (like the Navier-Stokes equation for fluids).
In fact, as John showed last week, we can't even properly describe static
piles. I will present results on granular shear flow experiments in
which we can measure particle trajectories and forces at the particle scale.
In particular, I'll show diffusivity and stored elastic energy measurements
which highlight the importance of the stress network that is unique to dense
flows. I'll describe why current statistical and hydrodynamic models
of granular materials are incomplete in light of these results and point
to ways in which we should expand current models.
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