Lattice Boltzmann modelling of contact angle and hysteresis under homogeneous and heterogeneous dynamic wetting regime

The contact angle is a measurement of wettability of a solid surface resulting from molecular attraction or repulsion at the encounter point between a liquid-gas interface and a wall. To date, the determination of the contact angle is commonly performed experimentally with very limited numerical modelling, due to the complex nature of the intermolecular forces at the liquid-gas-solid contact point, even in static conditions. This investigation presents the numerical modelling of the contact angle in static and dynamic conditions on homogeneous and heterogeneous wetting regimes using the multiphase Shan-Chen Lattice Boltzmann Model (SC-LBM). The dynamics of the phenomenon is modelled firstly through a statically suspended droplet and secondly through a sessile droplet subject to the shear flow of air. The Wenzel and Cassie-Baxter states are well reproduced as the response to surface roughness homogeneity. Numerical results demonstrate the excellent suitability of the multiphase SC-LBM for this problem. Furthermore, contact-angle hysteresis is determined under the homogeneous wetting dynamic regime. Two different motion modes were observed during the investigation of the contact angle hysteresis.