Capillary flow in nanoporous media: effective Laplace pressure

Imbibition dynamics in nanoporous media are explored using many-body dissipative particle dynamics for three types of nanoporous structures with varying porosities (ε), including random networks, periodic networks, and random voids. The permeability (ĸ) of the nanoporous structure is systematically determined through steady flow based on Darcy's law. The imbibition simulation outcomes align with the experimental results, demonstrating that the square of the penetration length (L²) is linearly proportional to time (t), L² = (S₁)t. The degree of imbibition rate, represented by S₁, is observed to increase with ε but remains insensitive to the pore structure, indicating the predominant role of viscous resistance over wettability-driven imbibition. The effective Laplace pressure, calculated from S₁, is used to estimate the effective pore diameter based on the Young-Laplace equation. The resultant diameter is considerably larger than the actual pore size. This finding implies that the driving force for imbibition in porous media is substantially weaker than it is in a capillary.