Surface roughness effect on dynamic wettability in imbibition process

Abstract

Dynamic wetting on rough surface is important in imbibition processes in micro- and nano- channels. Due to high computational costs, the previous studies by direct numerical simulations mostly adopted two-dimensional (2D) simplifications of surface with roughness. The cutting-edge advances in high performance computing make it possible to conduct three-dimensional (3D) direct simulations. This work presents 3D simulations on channel flows with roughness on walls via the GPU-based multiphase lattice Boltzmann method (LBM). The effects from 3D roughness morphology are investigated. In contrast to the wettability alternation in 2D rough ones, the 3D rough hydrophilic surfaces remain hydrophilic and Wenzel state at even low capillary numbers (Ca). The apparent contact angle follows the hydrodynamic model on rough surfaces except for a more sensitivity to Ca. The results also indicate that the 2D simplifications overestimate the pressure drop for rough channels, while underestimate over 20% for smooth channels. Therefore, it is crucial to consider 3D structures of surface roughness for dynamic wetting in real channels.