Improved pseudopotential lattice Boltzmann model to prevent droplet coalescence: from emulsion to dry foam
Résumé
In this paper, we propose a droplet non-coalescence method based on the lattice Boltzmann (LB) pseudopotential model. Due to its simplicity, the pseudopotential model has been widely used to simulate multiphase flows. However, with the original pseudopotential model, droplets in contact tend to merge, which poses a limitation in simulating densely packed droplets without coalescence, as observed in emulsions and foams. To overcome this limitation, our aim is to develop a noncoalescence method that does not introduce additional sets of distribution functions to simulate a stable system of droplets in close contact. In this proposed method, all droplets must be labeled with unique indexes, enabling the identification of each droplet, and pseudopotential repulsions are applied at droplet contacting interfaces to prevent them from merging. Although this approach effectively prevents droplet coalescence, there is a small amount of mass transfer between droplets. To correct this, we also incorporate a mass control scheme. It is found that the proposed method is able to model stable highly concentrated suspensions (HCS) with or without density and viscosity ratios. Besides, the proposed method can also simulate flowing HCS with arbitrarily high volume fractions of the dispersed phase allowing to simulate closely packed microfluidic soft flowing crystals or foams.
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