Simulation of bubble motion under gravity by lattice Boltzmann method

We describe the numerical simulation results of bubble motion under gravity by the lattice Boltzmann method(LBM), which assumes that a fluid consists of mesoscopic fluid particles repeating collision and translation and a mul tiphase interface is reproduced in a self-organizing way by repulsive inter action between different kinds of particles. The purposes in this study are to examine the applicability of LBM to the numerical analysis of bubble mo tions, and to develop a three-dimensional version of the binary fluid model that introduces a free energy function. We included the buoyancy terms due to the density difference in the lattice Boltzmann equations, and simulate d single- and two-bubble motions, setting flow conditions according to the Eotvos and Morton numbers. The two-dimensional results by LBM agree with th ose by the Volume of Fluid method based on the Navier-Stokes equations. The three-dimensional model possesses the surface tension satisfying the Lapla ce's law, and reproduces the motion of single bubble and the two-bubble int eraction of their approach and coalescence in circular tube. These results prove that tile buoyancy terms and the 3D model proposed here are suitable, and that LBM is useful for the numerical :analysis of, bubble motion under gravity.