Squeeze flow of highly concentrated suspensions of spheres

The squeeze flow behaviour of highly concentrated suspensions of spheres in a Newtonian fluid is studied experimentally. Analysing the evolution of the squeeze force as a function of time for different controlled velocities, the suspension is found to present two main flow regimes. The first regime is characterised by the situation in which the force decreases when the velocity decreases, which corresponds to a viscous flow of the suspension. In the second regime, the force increases when the velocity decreases, which is shown to correspond to a filtration of the solvent through the particle skeleton that behaves then as a deformable porous media. By varying the concentration, the sphere diameter and the solvent viscosity, it is found that the transition between the two regimes is a result of a competition between the viscous shear forces due the flow of the suspension and the damping force caused by the filtration of the fluid through the porous media made up by the particles.