Pore-scale prototypes of multiphase flow in porous media

Understanding the motion of immiscible fluids in porous media is a challenging problem in low-Reynolds-number hydrodynamics that is relevant to many processes of technological and biological interest. Simple representations of the flow on the scale of individual pores or channels have proven useful in exposing effects of various parameters on fluid motion and in identifying flow-induced changes in the spatial configurations of the fluids, which can affect the mobilities of the phases. This paper examines a hierarchy of such prototype flows, paying special attention to phenomena that cannot be described completely by the equations of motion, such as flow-induced breakup and coalescence of fluid phases. In these cases, connections between numerical computations and experiments are especially significant, which is apparent in the studies reviewed here.