Transport and sedimentation of suspended particles in inertial pressure-driven flow

The dynamics of flowing suspensions of spherical particles in a channel, including their sedimentation under gravity, is studied using lattice Boltzmann simulations. Spherical particles confined to a three-dimensional periodic channel of constant width are driven through it by an applied pressure gradient while gravity acts to deposit the particles on the bottom wall. The particle diameter is 1/10 the channel width and bulk concentrations varying from 0.13 to 0.34 are considered. The simulations cover a range of buoyancy and Reynolds numbers and include the effects of inertia. In the neutral buoyancy case, we observe concentration profiles peaked at the center of the channel, plus secondary peaks near the walls due to layering effects, and velocity profiles which become increasingly blunted as particle concentration rises. Gravity produces a three-layer system with clear fluid, flowing suspension, and dense sediment regions having parabolic, pluglike, and nearly stagnant velocity profiles, respectively. In most cases, the fluid and particle fluxes decrease and the clear fluid region width increase with gravitational forcing, although nonmonotonic behavior is observed in some cases.

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