Lattice Boltzmann modeling of buoyant rise of single and multiple bubbles

Buoyant rise of bubbles is investigated using the lattice Boltzmann method (LBM) based Gunstensen's color model. An external force/sink term is incorporated in the collision step to simulate buoyant rise of bubbles under gravitational force. The shape of a bubble is controlled by inertial, viscous and surface tension forces. The interplay between these forces is quantified using non-dimensional numbers such as Eötvös number (Eo), Morton number (Mo) and Reynolds number (Re). A set of results from numerical simulations are presented to demonstrate the ability of the proposed approach to simulate rise of single and multiple bubbles under buoyancy. The proposed modification is verified by comparing terminal velocity of bubbles in an infinite medium against the analytical solution. The shape of bubbles in various flow regimes characterized by the non-dimensional numbers is compared against the experimental data. The effect of surface tension and viscosity ratio on terminal velocity and shape of bubbles is investigated. The LBM results for topological change in the shape of bubbles or circularity of bubbles is compared against COMSOL. Co-axial and oblique coalescence of two gas bubbles are simulated and compared against the experimental data. The simulation results from LBM simulations were found to be in good agreement with the analytical solution, the experimental data and the COMSOL simulation.