Deformation-driven mixing in a soft porous medium*

Soils, textiles, gels, and biological tissues are porous and very soft. In these materials, deformation and fluid flow are strongly coupled through rearrangements of the pore structure. The resulting flow fields, which are both heterogeneous and unsteady, can play a key role in the transport and mixing of solutes in practical problems such as groundwater contamination and tissue engineering. Here, we use a continuum model based on large-deformation poroelasticiy to study the impact of periodic squeezing on solute transport and mixing in a soft porous medium. Transport occurs through advection, molecular diffusion, and hydrodynamic dispersion, each of which interacts differently with the deformation. We identify the key dimensionless control parameters, explore the resulting deformation and transport regimes, and consider the implications of preliminary experimental results.