Kinetics and Shape of a Sedimentary Jamming Front

Sedimenting grains form a planar jamming front that propagates upward as grains collect into a solid packing at the bottom of a column. The shape of the front may be stationary for tall samples at early times, but at later times this breaks down front interplay between the jamming front and the suspension-supernatant front. Here we obtain the spatiotemporal change of concentration profile for sedimenting non-Brownian particles in an index-matched fluid at low Reynolds numbers using light-sheet fluorescence imaging. Accordingly, shape of the one-dimensional jamming front is measured as a function of initial concentration. The empirically measured shape of the jamming front between sediment and suspension is compared with numerical solution of our formulated nonlinear partial differential sedimentation equation. This equation is based on the permeability of the suspension (a.k.a. the hindered settling function), a nonlocal lubrication force acting in proportion to the spatial gradient in the time derivative of volume fraction, plus gravity and mass conservation [1].
[1] C. P. Ortiz, T. A. Brzinski III, D. J. Durian, Nonlocal Lubrication Forces and the Sedimentary Jamming Front, arXiv:1710.09314 (2017).