Contact angles in the pseudopotential lattice Boltzmann modeling of wetting

TL;DR

This paper compares different fluid-solid interactions in pseudopotential lattice Boltzmann models to accurately simulate a wide range of contact angles, especially large static contact angles, in multiphase flow simulations.

Contribution

It introduces a modified pseudopotential-based interaction that improves simulation of large contact angles and compares it with existing methods in terms of accuracy and stability.

Findings

Pseudopotential-based interaction is effective for small contact angles.

Modified interaction better simulates large contact angles.

Increasing viscosity ratio reduces spurious currents.

Abstract

In this paper, we aim to investigate the implementation of contact angles in the pseudopotential lattice Boltzmann modeling of wetting at a large density ratio. The pseudopotential lattice Boltzmann model [X. Shan and H. Chen, Phys. Rev. E 49, 2941 (1994)] is a popular mesoscopic model for simulating multiphase flows and interfacial dynamics. In this model, the contact angle is usually realized by a fluid-solid interaction. Two widely used fluid-solid interactions: the density-based interaction and the pseudopotential-based interaction, as well as a modified pseudopotential-based interaction formulated in the present paper, are numerically investigated and compared in terms of the achievable contact angles, the maximum and the minimum densities, and the spurious currents. It is found that the pseudopotential-based interaction works well for simulating small static (liquid) contact angles, however, is unable to reproduce static contact angles close to 180 degrees. Meanwhile, it is found that the proposed modified pseudopotential-based interaction performs better in light of the maximum and the minimum densities and is overall more suitable for simulating large contact angles as compared with the other two types of fluid-solid interactions. Furthermore, the spurious currents are found to be enlarged when the fluid-solid interaction force is introduced. Increasing the kinematic viscosity ratio between the vapor and liquid phases is shown to be capable of reducing the spurious currents caused by the fluid-solid interactions.