A new wetting boundary scheme in phase-field lattice Boltzmann model for two-phase flows with large density ratios and complex solid boundaries

A new wetting boundary scheme for simulating large-density-ratio two-phase flow with complex solid boundary is developed within a modified phase-field lattice Boltzmann model. Compared to the existing schemes, the proposed method directly calculates the order-parameters gradient at boundary fluid nodes without estimating the order parameters of ghost solid nodes, and it possesses both the simplicity of geometrical formulation scheme and the accuracy of free-energy scheme. Additionally, a new method for identifying solid boundary contours is proposed, enabling the presented boundary treatment to handle arbitrary complex and irregular solid boundaries. Five benchmark cases are used to test the proposed method, including droplet spreading on a circular wall, capillary-driven flow between parallel plates, droplet impacting on a circular cylinder, capillary rise in sinusoidal wavy channels, and irregularly bounded porous media flow. The results show that the present method provides an accurate, efficient, and stable tool for simulating two-phase flows through complicated geometries at large density ratios.