Enhanced sedimentation of suspensions in porous media

It is demonstrated that the sedimentation rate of a suspension can be enhanced by a factor of about 2-8 if the suspension is placed inside a porous medium. Experiments were performed with suspensions of red blood cells inside glass tubes packed with glass beads, both under the effect of gravity and in a centrifuge. The enhancement factor is shown to depend on the packing of the porous medium, on the volumetric concentration of the suspension, and on the rigidity of the red blood cells. It seems independent of the material of which the beads are made.