Controlling capillary fingering morphology in patterned porous media

We present a methodology to modulate immiscible fluid-fluid invasion patterns in patterned porous media during drainage in the capillary fingering flow regime. A 2D patterned porous medium is generated by a sequential deposition algorithm of disks/grains of two distinct size ranges (dual-porosity media). To attain patterned porous media, selected regions are packed with small grains, elsewhere packed with larger grains. By tuning the ratio of viscous to capillary forces, as defined by the capillary number (Ca), we control the degree to which the underlying microstructure affects the invasion morphology in the patterned porous medium. A decrease in Ca amplifies the influence of the underlying pore structure, resulting in a more pronounced alignment of the flow pattern with the porous medium's geometry. For these “structured” flows, the drainage within zones packed with smaller grains (having relatively smaller pores) is less than 10%. In contrast, an increase in Ca promotes more “random” displacement patterns with significant invasion in fine (more than 10%) and coarse pores. The possibility to modulate multiphase flows using patterned porous media can have practical implications in engineered membrane designs for fuel cells, selective transport, and filtering applications.