On a modified pseudopotential lattice Boltzmann model for multicomponent flows

This paper presents a pseudopotential lattice Boltzmann model for multicomponent flows involving large viscosity ratios. Firstly, a rigorous Chapman–Enskog analysis is conducted to show that previous models cannot recover the correct governing equation with a single-relaxation-time scheme when the viscosity ratio is not unity. Then, based on this analysis, we established a modified model to obtain the correct governing equation by introducing a system relaxation time into the evolution equation. Finally, we validated the modified model by conducting a two-phase cocurrent (Poiseuille) flow with single-relaxation-time and multiple-relaxation-times schemes. The numerical results show that the present model enormously improves the range of the accessible viscosity ratio. For the single-relaxation-time scheme, the viscosity ratio ranges from 1∕250 to 250 with a fourth order isotropy. For the multiple-relaxation-times scheme, the viscosity ratio is numerically stable and accurate for viscosity ratios between 1∕1000 to 1000 with fourth order isotropy.