Improved extrapolation-based curved boundary schemes in pseudopotential multiple-relaxation-time lattice Boltzmann method for multiphase simulations

Curved boundary in multiphase flow simulations remains a formidable challenge for the lattice Boltzmann method. This is fraught with problems such as mass leakage and spurious currents. To address these issues, the present work proposes two improved curved boundary schemes by introducing non-ideal force into two extrapolation-based schemes (i.e., Mei-Luo-Shyy scheme and Guo-Zheng-Shi scheme), followed by mass-conservation correction. Moreover, an additional term is introduced. The accuracy and mass conservation of the two proposed boundary schemes are thoroughly validated through two two-dimensional numerical tests of droplet resting on a circular cylinder and boiling on a circular cylinder. The present improved schemes strictly not only ensure exact (i.e., 100%) mass conservation, even under the condition at large density ratio, but also have improved in terms of the spurious current and momentum conservation error. Furthermore, the present improved schemes are suitable for simulating boiling on curved surfaces.