Gaseous flow through ultra-tight porous media, e.g. shale and some high-performance insulation materials, is often rarefied, invalidating an analysis by the continuum flow theory. Such rarefied flows can be accurately described by the kinetic theory of gases which utilizes the Boltzmann equation and its simplified kinetic models. While discrete velocity methods have been successful in directly solving these equations, the immense potential of a particle-based solution of the variance-reduced Boltzmann-BGK (Bhatnagar–Gross–Krook) equation for rarefied flows in porous media has not been exploited yet. Here, a parallel solver based on the low variance deviational simulation Monte Carlo method is developed for 3D flows, which enables pore-scale simulations using digital images of porous media samples. The unique advantage of this particle-based formulation is in providing additional insights regarding the multi-scale nature of the flow and surface/gas interactions via two new parameters, i.e. pore and surface activity, respectively. Together, these two parameters can identify key flow properties of the porous media. The computational efficiency and accuracy of the current method has also been analysed, suggesting that this new solver is a powerful simulation tool to quantify flow properties of ultra-tight porous media.

通过超紧密多孔介质（例如页岩和某些高性能绝热材料）的气流通常被稀少，这使连续流理论的分析无效。这种稀疏流动可以通过利用玻尔兹曼方程及其简化的动力学模型的气体动力学理论来准确描述。尽管离散速度方法已经成功地直接求解了这些方程，但尚未开发出基于粒子的，减少了方差降低的Boltzmann-BGK（Bhatnagar-Gross-Krook）方程的多孔介质稀疏流动的巨大潜力。在此，针对3D流量开发了基于低方差偏差模拟蒙特卡洛方法的并行求解器，该并行求解器可以使用多孔介质样本的数字图像进行孔隙尺度模拟。这种基于颗粒的配方的独特优势在于，可以通过两个新参数（分别是孔隙和表面活性）提供有关流动和表面/气体相互作用的多尺度性质的更多见解。这两个参数一起可以确定多孔介质的关键流动特性。还分析了当前方法的计算效率和准确性，这表明该新求解器是量化超紧密多孔介质流动特性的强大仿真工具。