Abstract

In this work, a hybrid method coupling a pseudo-potential lattice Boltzmann model (LBM) and a pore network model (PNM) to simulate drying in porous media is proposed. Based on the watershed method, the porous medium is firstly decomposed into pore regions. According to the liquid–vapor phase distribution at a given time, the pore regions are further divided into four pore types, namely two-phase pores where a liquid–vapor interface exists, buffer pores next to the two-phase pores, single-liquid and single-vapor phase pores. The pseudo-potential LBM is used in the two-phase and buffer pores to simulate liquid drying and track the movement of the interfaces, while the single-phase PNM simulations are conducted in the buffer and single-phase pores to simulate vapor or liquid flow. LBM and PNM are coupled in the buffer pores through exchange of boundary information. The hybrid method is applied to simulate liquid drying in a porous medium. The whole-domain LBM simulation is considered as the reference solution to validate the hybrid method. Liquid saturation variation during the drying process and detailed phase and pressure distributions obtained by the two methods match quite well, demonstrating the accuracy of the hybrid method. For the specific case studied, the hybrid method saves more than 60% computational time compared to the whole-domain LBM simulation. In addition, the speedup of the hybrid method becomes more significant for a larger computational domain. In summary, the hybrid method developed in this work combines the accuracy of LBM and the efficiency of PNM to simulate drying in porous media at pore scale and can lead to significant reduction of computation time, thus allowing the pore-scale consideration of drying in larger porous systems.

摘要

在这项工作中，提出了一种耦合赝势格子玻尔兹曼模型（LBM）和孔隙网络模型（PNM）的混合方法来模拟多孔介质中的干燥。基于分水岭法，首先将多孔介质分解为孔隙区域。根据给定时间的液相-气相分布，将孔隙区域进一步划分为4种孔隙类型，即存在液-汽界面的两相孔、紧邻两相孔的缓冲孔、单液孔和单气相孔。赝势LBM用于两相和缓冲孔隙中模拟液体干燥和跟踪界面的运动，而单相PNM模拟在缓冲和单相孔隙中进行模拟蒸汽或液体流动. LBM 和 PNM 通过交换边界信息在缓冲孔中耦合。混合方法用于模拟多孔介质中的液体干燥。全域 LBM 仿真被认为是验证混合方法的参考解决方案。两种方法在干燥过程中的液体饱和度变化与详细的相位和压力分布非常吻合，证明了混合方法的准确性。对于所研究的特定案例，与全域 LBM 仿真相比，混合方法节省了 60% 以上的计算时间。此外，对于更大的计算域，混合方法的加速变得更加重要。总之，