Simulation of bubble-bubble interaction using a lattice Boltzmann method

This paper presents the results obtained from three-dimensional numerical simulations of multiple bubbles rising under buoyancy in a quiescent viscous incompressible fluid. A lattice Boltzmann method, based on the free-energy model, is developed to simulate the behavior of bubble-bubble interaction while rising in the fluid. A new scheme, which involves eighteen lattice points for the first and second derivative, is proposed to achieve stable computations at high fluid-to-bubble density ratio. The effects of the density ratio and the initial bubble configuration on the flow field induced by rising bubbles and on the evolution of bubble shape during their coalescence are investigated. It is found that for two rising bubbles with the same size, the leading bubble rises like an isolated bubble before coalescence. The trailing bubble is entrained by the leading one, and experiences obvious deformation when it enters the wake region of the leading bubble. The shape evolution of the trailing bubble is different at the high and low density ratios. However, for two rising bubbles with different sizes, the larger bubble always has strong effect on the smaller one in any initial configuration. (C) 2009 Elsevier Ltd. All rights reserved.