Getting Out Of A Tight Spot: Physics Of Flow Through Porous Materials

We study the physics of flow through porous materials in two different ways: by di-rectly visualizing flow through a model three-dimensional (3D) porous medium, and by investigating the deformability of fluid-filled microcapsules having porous shells. In the first part of this thesis, we develop an experimental approach to directly visu-alize fluid flow through a 3D porous medium. We use this to investigate drainage, the displacement of a wetting fluid from a porous medium by a non-wetting fluid, as well as secondary imbibition, the subsequent displacement of the non-wetting fluid by the wet-ting fluid. We characterize the intricate morphologies of the non-wetting fluid ganglia left trapped within the pore space, and show how the ganglia configurations vary with the wet-ting fluid flow rate. We then visualize the spatial fluctuations in the fluid flow, both for single- and multi-phase flow. We use our measurements to quantify the strong variability in the flow velocities, as well as the pore-scale correlations in the flow. Finally, we use our experimental approach to study the simultaneous flow of both a wetting and a non-wetting fluid through a porous medium, and elucidate the flow instabilities that arise for sufficientl