Three-dimensional modeling of coalescence of bubbles using Lattice Boltzmann model

Abstract

The original Lattice Boltzmann method (LBM) based binary color model is modified to simulate three-dimensional buoyant multiphase flow. An effective force term is included during collision step in D3Q19 LBM to account for buoyancy force due to density contrast between fluid components. Buoyancy is not directly simulated as an effect of pressure gradients in the flow but was introduced from an analytical understanding of buoyancy effects due to density difference between the two phases. We are presenting results from three-dimensional numerical simulations to demonstrate the ability of the proposed approach to accurately predict the behavior of a single and multiple bubbles in a buoyant multiphase flow system. The effect of parameters such as grid size, viscosity ratio, surface tension, and interfacial thickness on the model accuracy are presented in this article. The shape and terminal velocity of bubbles in various flow regimes, characterized by the non-dimensional numbers (Eo, Mo, Re), are compared against experimental data and analytical model. The 3-D simulation results of Co-axial and oblique coalescence of a pair of bubbles from LBM simulations were found to be in good agreement with the experimental data.