Pore network simulation of fluid imbibition into paper during coating—III: modelling of the two-phase flow

Extensive computer simulations have been carried out to model imbibition of a coating fluid into a paper. The microstructure of the paper's pore space is represented by a network of interconnected channels or pore throats that are formed between the paper's fibers. The geometrical characteristics of the channels, such as their effective radius and length, as well as their connectivity, are selected from the experimental data presented in Part II of this series. The imbibition process that we simulate is the result of forcing the coating fluid into the pore space by applying a time-dependent flow-driven pressure distribution to the external surface of the paper, or is driven only by capillary forces. The dynamic pressure distribution is representative of a high-speed coating process. The simulations indicate that the connectivity of the pore throats, the anisotropic structure of the paper's pore space, and the dynamic pressure distribution all have a strong influence on imbibition of a coating fluid into a paper's pore space and, hence, on the quality of the coating.