An improved phase-field-based lattice Boltzmann model for droplet dynamics with soluble surfactant

•The phase-field lattice Boltzmann model is improved to simulate two-phase flows with soluble surfactant.•The two-phase interfacial profile is independent of surfactant concentration in the model.•The surfactant can promote droplet deformation and accelerate the droplet breakup.•The surfactant leads...

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Veröffentlicht in:Computers & fluids 2019-01, Vol.179, p.508-520
Hauptverfasser: Shi, Y., Tang, G.H., Cheng, L.H., Shuang, H.Q.
Format: Artikel
Sprache:eng
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Zusammenfassung:•The phase-field lattice Boltzmann model is improved to simulate two-phase flows with soluble surfactant.•The two-phase interfacial profile is independent of surfactant concentration in the model.•The surfactant can promote droplet deformation and accelerate the droplet breakup.•The surfactant leads to less coalescence of multiple droplets and more complex interactions. We present an improved phase-field model in the lattice Boltzmann scheme to investigate the droplet dynamics in the presence of soluble surfactant. The phase-field model based on the Ginzburg–Landau free energy is developed in which the immiscible binary fluid interfacial profile is independent of the surfactant concentration. The improved model is validated and then employed to study the surfactant effect on single droplet deformation, two droplets interactions and interactions among four droplets in the shear flow. The results show that the increase of surfactant concentration promotes droplet deformation, droplet breakup and more complex droplet-droplet interaction compared to the clean droplet. Moreover, the effects of capillary number, viscosity ratio, as well as peclet number on the behavior of surfactant-covered droplets in the shear flow are investigated. The results indicate that the droplet Taylor deformation parameter increases with the increase of capillary number but the decrease of viscosity ratio. The minimum distance between two interacting droplets enlarges with both capillary number and peclet number.
ISSN:0045-7930
1879-0747
DOI:10.1016/j.compfluid.2018.11.018