Effect of porous media models on rheological properties of suspensions

This work reports an experimental investigation of the flow of non-colloidal, non-Brownian suspensions via rheological tests over and through well-designed porous media models. We performed a series of simple shear flow experiments using a rheometer with a parallel-plate geometry where different porous structures were placed on the lower plate. The impact of various bulk particle volume fractions of suspensions phi(b), ranging from 0 to 0.4, was studied by considering four different porous microstructures with porosities of 0.7 and 0.9. We designed and built porous media models with known permeability and porosity, where the particles were either allowed to move or prevented from moving inside the porous structures. We examined the impact of viscosity by the existence of porous media. We found that, when particles move inside the porous layer, the slip velocity at the fluid-porous interface increases and varies with the porosity compared to when they do not flow into the porous layer. Additionally, with the increase in volume fraction of suspensions, the slip velocity decreases at a constant stress while the slip length rises. We then compared these data with the volume-averaged Navier-Stokes (VANS) equations for flow in the porous medium coupled with the Stokes equations in the free-flow region to further examine the slip velocity.