Abstract: Equilibrium distribution functions for lattice model D3Q15 are proposed in the framework of lattice Boltzmann method in free energy model. Bubble merging process is studied. It shows that bubble merging not only depends on initial bubble distance, but also depends on surface tension. The greater the surface tension is, the greater the critical distance for bubble merging. Furthermore, influence of initial bubble distance, surface tension and viscosity on merging velocity are investigated.

Key words: bubble merging, lattice Boltzmann method, surface tension, gas-liquid interface