Saturation Modeling in 3D Fibrous Media
The biggest challenge in the field of coalescence filtration is to predict the transient or steady-state saturation of the filter and to predict filtration performance at that saturation. Obtaining the saturation field of a filter by conventional CFD methods (e.g., volume-of-fluid) is computationally expensive. In this work, we implemented a computationally affordable Pore Morphology Method (PMM) to obtain a steady-state saturation field in the filter. The PMM employs morphological operations such as dilation and erosion to emulate the intrusion of a non-wetting phase (NWP) in a media filled with wetting-phase (WP). The PMM algorithm is shown in the figure below,
The predictions of PMM simulations were compared with volume-of-fluid (VOF) and energy minimization method (EMM) and it was found that PMM always overestimated the intrusion pressure, partly because it cannot detect coalescence failure. Moreover, the predictions suffers in media with high aspect ratio pores.
The PMM algorithm always marks the largest geometrical pore in the domain as the location from which a NWP penetrates into the saturated media and that the NWP entry point is independent of the contact angle of the media (as long as all solid surfaces have the same contact angle), which is not an accurate simulation of real physics.
However, for disordered fibrous media (like a coalescing filter) the intrusion pressure prediction by the PMM was close to the VOF method as it is less likely for the pores in a randomly oriented fibrous structure to have high aspect ratios. The PMM can be used to obtain media at different levels of saturation.
Although the PMM simulations were less accurate, they were orders of magnitude faster than their VOF counterparts. This makes the PMM an appealing choice for saturation modeling in complex 3D porous structures (e.g., coalescing filters, packed bed reactors, barrier fabrics, etc.), where the 3D fluid saturation profile in the media is desired.