Introduction

Multiphase fluid phenomena and flows occur when two or more fluids that do not readily mix (such as air and water) share an interface. Computational fluid dynamics (CFD) has become very important in fluid flow studies. The Lattice Boltzmann method (LBM) has developed very quickly in the last two decades and has become a novel and powerful CFD tool, particularly for multiphase flows. In the LBM, the more fundamental Boltzmann equation is directly discretized. Compared to common CFD methods, the LBM has many advantages. It is based on the molecular kinetic theory, and for single-phase flow simulations it usually involves an ideal-gas equation of state. This chapter provides an introduction to several popular multiphase LBM models that include: the Color-gradient model, Shan–Chen model, Free-energy model, and the Interface tracking model. All the above Lattice Boltzmann multiphase models are under active development.