PIV measurements of dilute suspension flows over porous medium models

Porous media encompasses a variety of materials, with unique engineering applications. This study specifically examines pressure-drive flow of dilute suspensions ranging from particle volume fractions of 0.01 to 0.03 over porous media. We consider the flow of neutrally buoyant, non-colloidal, non-Brownian suspensions of rigid, spherical particles in a Newtonian fluid when both particle and suspension Reynolds number are very low. The porous media was designed to have varying porosities ranging from 0.3 to 0.9 in order to show how the structure of the media affects the flow dynamics. To analyze the coupled flow and to conduct detailed velocity measurements inside and over the porous media models, we utilized particle image velocimetry (PIV). We also characterized the slip velocity at the interface of the porous media and the suspension flow. It was found that values of the slip velocity normalized by either the maximum velocity or by shear rate in the free flow region depend on the property and the thickness of porous media, the size and concentrations of the particles in the suspension. We also discuss in detail the comparison between the experimental data and our theoretical models.