Pseudopotential-based discrete unified gas kinetic scheme for modeling multiphase fluid flows

Abstract

By coupling the pseudopotential model into the discrete unified gas kinetic scheme (DUGKS), we develop a concise kinetic approach for modeling multiphase fluid flows at the mesoscopic level. To eliminate the influences of non-isotropic terms introduced during the reconstruction process, the expression of equilibrium distribution functions is reformulated in a moment-based form. With the isotropy-preserving parameter appropriately tuned, the non-isotropic effects can be perfectly canceled out. The proposed pseudopotential-based DUGKS managed to produce and maintain isotropic interfaces. The fundamental capabilities are validated by the flat interface test and the quiescent droplet test. The isotropy-preserving property of pseudopotential-based DUGKS in transient conditions is further confirmed by the spinodal decomposition. Stability superiority of the pseudopotential-based DUGKS over the lattice Boltzmann method is also demonstrated by predicting the coexistence densities complying with the van der Waals equation of state.

Free-Energy-Based Discrete Unified Gas Kinetic Scheme for van der Waals Fluid

“…However, the DUGKS studies centered on multiphase fluid flows remain limited [ 47 , 48 ] and the multiphase DUGKS has been primarily confined to the phase-field model [ 49 ]. Although Yang et al [ 50 ] developed a pseudopotential-based DUGKS for binary fluid flow, a free parameter is needed to guarantee the isotropic property of the fluid interface. Inspired by the well-balanced LB scheme [ 30 ], Zeng et al [ 51 ] proposed a well-balanced DUGKS for two-phase fluid flows using the free-energy model.…”