Multiphase Lattice Boltzmann Method: Computational Framework and Implementation Approaches

In multiphase flow research, the Shan-Chen type lattice Boltzmann method (LBM) provides an efficient computational framework for simulating complex two-phase flows. The method introduces pseudopotential functions to describe interphase interactions through density-based force calculations, naturally capturing interface dynamics without explicit interface tracking algorithms. Viscous coupling effects represent critical factors influencing two-phase flow behavior. When fluids with different viscosities interact, velocity gradients at the interface cause additional momentum transfer. The Shan-Chen model effectively captures this viscous coupling phenomenon by modifying the collision operator and implementing density-dependent relaxation times, typically coded through BGK collision terms with variable tau parameters. Research demonstrates that viscosity ratios significantly impact interface stability: high viscosity ratios may cause interface fluctuations, while appropriate adjustment of pseudopotential strength can suppress unphysical oscillations. This method proves particularly suitable for microscale flows, where the relative importance of surface tension and viscous forces can be quantitatively characterized through dimensionless numbers like the capillary number. In extended applications, the method can integrate with wettability models to study contact angle effects using boundary condition modifications, or incorporate temperature fields for phase transition simulations through additional distribution functions, providing a unified solving framework for multiphysics coupling problems. Code implementation typically involves multiple distribution functions for different physical fields and coupled force terms in the streaming step.