Dynamic balance of the mesoscale repulsion and attraction with varying surface tension and interaction coefficients on two-phase flow patterns simulated by an improved non-dimensional lattice Boltzmann model

Abstract

An improved mesoscale two-phase flow non-dimensional lattice Boltzmann model (NDLBM) is developed for simulating dynamic balance effects of varying surface tension and interaction coefficients. The mesoscale surface tension coefficient is related to the ratio of surface tension strength to the product of the mesoscopic length scale and the equilibrium particle group size. Relative attraction and repulsion strengths among fluid particles of both different and same phases are modeled by positive and negative interaction coefficients, respectively. Both macroscopic and mesoscopic governing parameters are expressed with physical properties for each coefficient. Three basic types (liquid crystal, viscous fluid, and chain rod vorticity patterns) and two combined types (lattice viscous and stretched viscous vorticity patterns) are observed. Phase volume fraction distributions and vorticity structure patterns are illustrated to show the underlying mechanism of the balance effects of the mesoscale repulsion and attraction. The full map is shown with division curves of different pattern regimes of key mesoscale coefficients, and the division curves quantitatively show how the coefficients affect the transition of flow patterns.