Wetting boundary condition for the color-gradient lattice Boltzmann method: Validation with analytical and experimental data

Abstract

a b s t r a c tIn the color gradient lattice Boltzmann model (CG-LBM), a fictitious-density wetting boundary condition has been widely used because of its ease of implementation. However, as we show, this may lead to inaccurate results in some cases. In this paper, a new scheme for the wetting boundary condition is proposed which can handle complicated 3D geometries. The validity of our method for static problems is demonstrated by comparing the simulated results to analytical solutions in 2D and 3D geometries with curved boundaries. Then, capillary rise simulations are performed to study dynamic problems where the three-phase contact line moves. The results are compared to experimental results in the literature (Heshmati and Piri, 2014). If a constant contact angle is assumed, the simulations agree with the analytical solution based on the Lucas-Washburn equation. However, to match the experiments, we need to implement a dynamic contact angle that varies with the flow rate.

Local Capillary Pressure Estimation Based on Curvature of the Fluid Interface – Validation with Two-Phase Direct Numerical Simulations

“…This results in a slightly diffusive interface whose thickness is about 2 to 3 lattice units. Further details of our LB model can be found in Akai et al [11,12]. The only difference is that we used the MRT collision operator, while the single-relaxation-time (SRT) collision operator [13] was used in Akai et al [11].…”

“…Further details of our LB model can be found in Akai et al [11,12]. The only difference is that we used the MRT collision operator, while the single-relaxation-time (SRT) collision operator [13] was used in Akai et al [11]. At solid-fluid boundary lattice nodes, a full-way bounce back boundary condition was implemented to achieve a non-slip boundary condition.…”

“…At solid-fluid boundary lattice nodes, a full-way bounce back boundary condition was implemented to achieve a non-slip boundary condition. In addition, the wettability of solid surface was modeled by specifying contact angles using the wetting boundary condition presented in Akai et al [11]. This wetting boundary condition accurately assigns contact angles for 3D arbitrary geometries with smaller spurious currents compared to the widely-used fictitious density boundary condition [11].…”

Mechanisms of Microscopic Displacement During Enhanced Oil Recovery in Mixed-Wet Rocks Revealed Using Direct Numerical Simulation

“…This spatially varying body force F is incorporated into the lattice Boltzmann equation through the body force term φ i using the forcing scheme proposed by Guo et al (2002). Further details of our LB model can be found in Akai et al (2018). At solid-fluid boundary lattice nodes, a full-way bounce back boundary condition is implemented to achieve the non-slip boundary condition.…”

“…At solid-fluid boundary lattice nodes, a full-way bounce back boundary condition is implemented to achieve the non-slip boundary condition. In addition, the wettability of solid surface is modeled by specifying contact angles using the wetting boundary condition presented in Akai et al (2018) which accurately assigns contact angles for 3D arbitrary geometries with smaller spurious currents compared to the widely used fictitious density boundary condition. A constant velocity and constant pressure boundary condition (Zou and He 1997) are applied at inlet and outlet boundary lattice nodes, respectively.…”