Lattice Boltzmann modeling of a gravity-driven sliding droplet under a dynamic wetting regime

This work presents the numerical modeling of a sliding droplet on a vertical smooth wall under hydrophobic and hydrophilic conditions using the multiphase Shan–Chen Lattice Boltzmann Model (SC-LBM). The gravitational action above the interfacial force was introduced through the variation of the Bond number and contact angle between droplet, solid surface and surrounding fluid. A critical Bond number, above which the droplet would keep indefinitely deforming, was found for different wettability conditions as well as density and viscosity ratios. The critical Bond number proved to be insensitive to the viscosity ratio (Fluid 1/ Fluid 2, Fluid 1: liquid; Fluid 2: gas), but largely dependent on the density ratio (Fluid 1/ Fluid 2, Fluid 1: liquid; Fluid 2: gas). The present SC-LBM results demonstrate the excellent suitability of the multiphase SC-LBM for the prediction of the dynamic contact angle and reproduction of the continuous droplet deformation and eventual breakup of a sliding droplet subject to gravity force.