An improved multi-component lattice Boltzmann method for simulation of gas-liquid flows with high density ratio

摘要

In recent years, the Lattice Boltzmann Method (LBM) has proved to be an effective approach for multiphase flow simulations. Unlike the traditional CFD methods which are based on the macroscopic mass and momentum balance equations, LBM is based on the mesoscale kinetic model of fluid molecules. When simulating two-phase flow problems, it does not require the interface-capturing or interface-tracking algorithms that are used in the traditional volume of fluid (VOF), level-set or front tracking methods. However, the use of LBM in realistic engineering applications is restricted because of some well-known weaknesses, such as the limited density ratio between the two phases. Several attempts have been made to enhance the stability of LBM at high density ratio. Inamuro et al. (2004) simulated two-phase flows with large density differences by solving the pressure Poisson equation with the free energy based LBM. They were able to obtain stable results at the density ratio of 1000. However, solving the pressure Poisson equation is very time consuming. Lee and Lin (2005) employed pressure evolution equation and simulated two-phase flows at density ratio of 1000. In their model, the discretization of the collision step was different before and after the streaming step, which also added to the computation expense. Recently, it has been shown by Yuan and Schaefer (2006) that the formulation of the interaction potential in the pseudo-potential based LBM has important effects on the density ratio range in a single-component system. By employing the appropriate interaction potential, which is related to the equation of state of the fluid, they were able to reach density ratio of 1000, without the need for complicated discretization or solving the Poisson equation.