Understanding droplet coalescence and transport dynamics in fibrous materials is critical for elucidating coalescence filtration mechanisms and enhancing filter efficiency. However, conventional experimental techniques face limitations in temporal and spatial resolution, hindering real-time monitoring of liquid transport phenomena within fibrous matrices. This study develops a numerical framework using cascaded multi-component Lattice Boltzmann Method to simulate coalescence-filtration processes in porous media[1], with particular emphasis on wettability-dependent coalescence behavior and transport mechanism. The results show that wettability plays a decisive role in the coalescence efficiency and transport mechanisms of filtration materials, as shown in Figure 10. For hydrophilic materials, droplets are more readily captured and gradually form stable liquid bridge structures. These structures not only reduce porosity to enhance droplet capture probability but also establish stable pathways for directional liquid transport. For hydrophobic materials, the captured droplets are more prone to detach from fibers, due to the weakened droplet-fiber adhesion, leading to diminished coalescence efficiency. Consequently, liquid transport primarily relies on coalesced droplets being gradually conveyed backward under the driving force of liquid flow. Given this, we propose a graded-wettability material architecture that enables the effective separation of immiscible fluids.
 

Coalescence filtration; Wettability; Transport processes;