Multiple-relaxation time color-gradient lattice Boltzmann model for simulating contact angle in two-phase flows with high density ratio

The contact line dynamics is an important phenomenon in natural and industrial processes and is still a challenging problem. The complexity of this problem in computational simulations is much more than theoretical and experimental works. In this paper, a color-gradient (CG) lattice Boltzmann method (LBM) for simulating wetting phenomena and the dynamics of contact line in two-phase flows with very high density-ratio (∼ 1000 was used. This method applies a multi-relaxation time (MRT) collision operator to enhance the stability of numerical scheme. Both static and dynamic contact angles were enforced at the wall through geometrical wetting boundary condition. Note, the main nobility of this paper is the supplementation of geometrical wetting boundary condition to the color gradient LBM and applying the present computational methodology for two-phase flow physics with a very high density ratio. This method is first validated by simulating a stationary drop and static contact angles. Also, the dynamical behavior of a drop on an ideal surface in shear flow was computationally validated. Finally, simulation of a drop motion subjected to gravitational force was the fourth test case studied. According to the results of these test cases, small values of spurious velocities and equilibrium contact angle errors were found in the simulations of steady cases studied. While, in our unsteady test cases, the behavior of the interface shapes and contact angles were in good agreements with previous reliable studies.