The fastest capillary flow under gravity

A single-layer porous structure composed of packed particles is designed to achieve the fastest capillary flow under gravity. The minimum flow time for a fixed flow distance is determined by dynamic competition between capillary pressure, gravity, and viscous effects, all of which have different sensitivities to local microstructures of the porous system. Optimal structural parameters are found that account for the minimum flow time in the single-layer porous medium. The theoretical results obtained can be used for the optimization of porous architectures, achieving excellent liquid management properties.