  We experimentally examine pressure-driven flows of 1%, 3%, and 5% dilute
suspensions over and through a porous media model. The flow of non-colloidal,
non-Brownian suspensions of rigid and spherical particles suspended in a
Newtonian fluid is considered at very low Reynolds numbers. The model of porous
media consists of square arrays of rods oriented across the flow in a
rectangular channel. Systematic experiments using high-spatial-resolution
planar particle image velocimetry (PIV) and index-matching techniques are
conducted to accurately measure the velocity measurements of both very dilute
and solvent flows inside and on top of the porous media model. We found that
for 1%, 3%, and 5% dilute suspensions the fully-developed velocity profile
inside the free-flow region are well predicted by the exact solution derived
from coupling the Navier-Stokes equation within the free flow-region and the
volume-averaged Navier Stokes (VANS) equation for the porous media. We further
analyze the velocity and shear rate at the suspension-porous interface and
compare these data with those of pure suspending fluid and the related
analytical solutions. The exact solution is used to define parameters necessary
to calculate key values to analyze the porous media/fluid interaction such as
Darcy velocity, penetration depth, and fractional ratios of the mass flow rate.
These parameters are comparable between the solvent, dilute suspensions, and
exact solution. However, we found clear effects between the solvent and the
suspensions which shows different physical phenomenon occurring when particles
are introduced into a flow moving over and through a porous media.
