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Pore-scale Simulation of Gas Flow in Microscopic Permeable Media with Complex Geometries
Gas Science and Engineering Pub Date : 2020-09-01 , DOI: 10.1016/j.jngse.2020.103441
Yuhang Wang , Saman A. Aryana

Abstract Lattice Boltzmann method (LBM) is an efficient tool to perform direct numerical simulation of gas flow in micro-size pores. Despite great advances in LBM and its use in describing gas flow in micro-size channels in slip and transitional flow regimes, exploring formulations that are able to capture flow behavior in domains with complex boundary geometries remains a challenging task. As a result, the impact of complexities in pore structures on gas flow may not be fully explored using LBM. In this study, we propose to use the combined bounce-back and Maxwellian diffusive reflection scheme to capture the slip velocity with a new set of slip coefficients. Optimal values of slip coefficients are determined using a gradient based method, where the results from the linearized Boltzmann equation is used as the reference solution. The proposed formulation is further validated against predictions from molecular dynamics simulation in the presence of complex geometries by introducing obstacles of different shapes in straight channels. LBM with the proposed boundary treatment is then used to investigate gas flow in a synthetic microscopic permeable medium. Results indicate that gas exhibits different flow configurations as Knudsen number varies, and apparent gas permeability appears to have up to a second-order dependency on the reciprocal mean pressure in slip and transitional flow regimes.

中文翻译:

复杂几何结构微观渗透介质中气体流动的孔隙尺度模拟

摘要 格子玻尔兹曼方法(LBM)是直接数值模拟微孔内气体流动的有效工具。尽管 LBM 在描述滑移和过渡流态下微型通道中的气流方面取得了巨大进步,但探索能够捕获具有复杂边界几何形状的域中的流动行为的公式仍然是一项具有挑战性的任务。因此,使用 LBM 可能无法充分探索孔隙结构的复杂性对气流的影响。在这项研究中,我们建议使用组合的反弹和麦克斯韦漫反射方案来捕获具有一组新滑移系数的滑移速度。滑移系数的最佳值是使用基于梯度的方法确定的,其中线性化 Boltzmann 方程的结果用作参考解。通过在直通道中引入不同形状的障碍物,在存在复杂几何形状的情况下,根据分子动力学模拟的预测进一步验证了所提出的公式。然后使用具有建议边界处理的 LBM 来研究合成微观可渗透介质中的气体流动。结果表明,随着克努森数的变化,气体表现出不同的流动形态,并且表观气体渗透率似乎对滑移和过渡流态中的倒易平均压力具有二阶依赖性。然后使用具有建议边界处理的 LBM 来研究合成微观可渗透介质中的气体流动。结果表明,随着克努森数的变化,气体表现出不同的流动形态,并且表观气体渗透率似乎对滑移和过渡流态中的倒易平均压力具有二阶依赖性。然后使用具有建议边界处理的 LBM 来研究合成微观可渗透介质中的气体流动。结果表明,随着克努森数的变化,气体表现出不同的流动形态,并且表观气体渗透率似乎对滑移和过渡流态中的倒易平均压力具有二阶依赖性。
更新日期:2020-09-01
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