A multiphase MPS method for bubbly flows with complex interfaces

Abstract

The bubbly flows have always been a key research object in the field of multiphase simulations. However, when the bubbly flows become violent to cause the large deformations of bubbles, complex interfaces may be generated and bring great challenges to the traditional mesh-based methods. To overcome this challenge, one of the most commonly used mesh-free particle methods - moving particles semi-implicit (MPS) method, is adopted in this paper for the numerical simulations of bubbly flows with complex interfaces. Firstly, a multiphase MPS method is developed by combining the single-phase improved MPS (IMPS) method proposed in our previous study with different multiphase models, including the improved density smoothing scheme, interparticle viscosity model, continuous acceleration model, surface tension model, incompressible-compressible model and multiphase collision model. Then, the deformations of 2D/3D square droplets are simulated to validate the surface tension model, and the multiphase MPS method is verified through the benchmark cases of 2D/3D single bubble rising with large density and viscosity ratios (up to 1000 and 100, respectively). Finally, a series of bubbly flows with increasing complexity are performed, including the bubble rising and breaking at a high Reynolds number, the co-axial coalescence of two bubbles with different radiuses, and the violent interactions between a set of bubbles. The MPS results keep fair agreements with other numerical and experimental results, through which the advantages of the present multiphase MPS method in bubbly flows with complex interfaces can be well demonstrated.