Dynamics of flowing air in partially water-saturated, porous geological formations are governed by a wide range of forces and parameters. These dynamics are reviewed in the contexts of flow patterns that arise and the corresponding applicability of diverse modeling approaches. The importance of reliable gas-liquid flow models draws from the key role gases play in earth systems, and the various engineering practices involving air injection into geological formations. Here, we focus on air flow in water-wet porous media. We survey the factors that affect flow patterns and phase configurations, and the measures that quantify them. For single-phase flow in saturated media (i.e., air flow in dry media or water flow in water-saturated media), the continuum approach (Darcy's law) is generally applicable and offers a good interpretive tool. However, the coupled two-phase flow continuum approach appears appropriate only for phase-saturation degrees that allow both phases to be continuous in the flow domain. Furthermore, air flow in wet media is highly unstable. As a result, air commonly flows in preferential pathways or in the form of bubbles and ganglia, which are not amenable to continuum modeling. On the other hand, pore-scale models that account for the complex geometries and interfaces between the fluids and the media require extreme computational efforts, and generally inaccessible details on medium characteristics. Other stochastically-based representations, such as percolation theory, have value in the conceptualization of complex flow problems but demonstrate limited success in interpreting phase configurations, saturation degrees, and relative permeabilities.

中文翻译：

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部分水饱和多孔介质中的气流动力学

在部分水饱和的多孔地质构造中流动的空气动力学受各种力和参数的控制。这些动态在出现的流动模式和不同建模方法的相应适用性的背景下进行审查。可靠的气液流动模型的重要性源于气体在地球系统中的关键作用，以及涉及将空气注入地质构造的各种工程实践。在这里，我们关注水湿多孔介质中的气流。我们调查了影响流动模式和相配置的因素​​，以及量化它们的措施。对于饱和介质中的单相流（即干燥介质中的空气流或水饱和介质中的水流），连续介质方法（达西定律）通常适用并提供了一个很好的解释工具。然而，耦合双相流连续体方法似乎仅适用于允许两相在流动域中连续的相饱和度。此外，湿介质中的气流非常不稳定。因此，空气通常在优先通道中流动或以气泡和神经节的形式流动，这不适合连续介质建模。另一方面，考虑复杂几何形状和流体与介质之间界面的孔隙尺度模型需要极端的计算工作，并且通常无法获得有关介质特性的详细信息。其他基于随机的表示，如渗流理论，在复杂流动问题的概念化方面具有价值，但在解释相配置、饱和度和相对渗透率方面取得的成功有限。