Numerical simulation of the droplet formation involving fluids with high viscosity ratio by lattice Boltzmann method

Abstract

A multiple-relaxation-time color gradient lattice Boltzmann model is established for simulating the flow mechanism of viscous fluids or fluids with high viscosity ratios in the microchannel. The regularized method is incorporated in this MRT framework to deal with the high viscosity ratio problems involving practical inlet–outlet boundaries. By taking several static and dynamic cases, we prove that this model could accurately describe interfacial tension, wettability, and flow problems in two-phase flows with a low spurious velocity at the range of viscosity ratio up to O(103). Using this model, we successfully simulate the droplet formation process of fluids with a high viscosity ratio in the common T-junction channel. The results are in good agreement with the experiments in the literature. We further investigate the effect of high viscosity ratios on the dispersion process, revealing that the substantial increase in terms of the viscosity ratio of fluids leads to the enhancement of continuous phase viscous shear and dispersed phase inertia effect, which would bring the deviation of the operating range from mostly reported flow systems.