Dense suspensions: solid-liquid interactions at the particle scale

Flows of solid-liquid suspensions span a multi-dimensional parameter space, with coordinates such as the Stokes number, the solids volume fraction, the density ratio, and Reynolds numbers. We are interested in systems with appreciable inertia effects - i.e., non-zero Stokes and Reynolds numbers - having density ratios of the order of one (typical for solid-liquid systems) and solids volume fractions of at least 0.1. Additional effects include strongly inhomogeneous solids distributions, non-Newtonian liquids, and sticky particles that tend to aggregate. This leads to a rich spectrum of interactions at the scale of individual particles. To reveal these we perform direct simulations of collections of a few thousand of particles carried by a liquid flow with resolution of the solid-liquid interfaces. For this we use the lattice-Boltzmann method supplemented with an immersed boundary approach.