Droplet formation and growth from fibrous porous media

Two phase flow in porous media has been extensively studied for its applications in oil recovery, CO2 storage, and other industrial processes. Much of the existing work focuses on flow patterns within the porous media, but the resultant emulsion once the two-phase flow passes through the media remains unexplored, despite its importance in various applications, such as coalescence filtration. In coalescence filtration, fibrous filter media are used to coalesce small droplets that are difficult to remove into larger ones that can be removed via sedimentation. Using a microfluidic setup, we investigate how the water (dispersed phase) and oil (continuous phase) flow rates through the filter media affect the produced droplet sizes. Using fluorescence imaging, we simultaneously visualize the water pathway inside the porous media and capture the formation and growth of droplets that emerge from the filter. Our experiments reveal the dependence of the droplet size on the fractional water flow rate, total flow rate, and the size of the pathway. We use mathematical modeling and simulations to explain these observations.