Squeeze flow of concentrated suspensions of spheres in Newtonian or shear-thinning fluids

The squeeze flow behaviour of concentrated suspensions of spheres in both Newtonian and shear thinning fluids is investigated 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 characterized by the situation in which the force decreases when the velocity decreases, which is expected and corresponds to a power-law fluid flow of the suspension. In the second regime the force increases when the velocity decreases which is an indication of solvent filtration through the particle skeleton that behaves then as a quasi-rigid porous media. 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. It is shown that the addition of a small amount (1000ppm) of a polymer (Xanthan) to the solvent significantly decreases the squeeze velocity for which we have fluid filtration.