Friday, June 28, 2013

1306.6445 (Q. Li et al.)

Achieving tunable surface tension in the pseudopotential lattice
Boltzmann modeling of interface dynamics

Q. Li, K. H. Luo
In this paper, we aim to address an important issue about the pseudopotential lattice Boltzmann (LB) model, which has attracted much attention as a mesoscopic model for simulating interfacial dynamics of complex fluids, but suffers from the problem that the surface tension cannot be tuned independently of the density ratio. In the literature, a multi-range potential was devised to adjust the surface tension [Sbragaglia et al., Phys. Rev. E, 2007, 75, 026702; Sbragaglia et al. Soft Matter, 2012, 8, 10773]. However, this approach was found to be unable to keep the density ratio unchanged when the surface tension is adjusted. An alternative approach is therefore proposed in the present work. The basic strategy is to add a new source term to the LB equation so as to tune the surface tension of the pseudopotential LB model. The proposed approach can guarantee that the adjustment of the surface tension does not affect the mechanical stability condition of the pseudopotential LB model, and thus provides a separate control of the surface tension and the density ratio. Meanwhile, it still retains the mesoscopic feature and the computational simplicity of the pseudopotential LB model. Numerical simulations are carried out for stationary droplets, capillary waves, and droplet splashing on a thin liquid film. The original Shan-Chen pseudopotential and the pseudopotential with a piecewise linear equation of state [Colosqui et al., Soft Matter, 2012, 8, 3798] are both considered. The numerical results demonstrate that the proposed approach is capable of achieving a tunable surface tension over a wide range and can keep the density ratio unchanged when adjusting the surface tension.
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