Inertial forces affect fluid front displacement dynamics in a pore-throat network model.
Inertial forces affect fluid front displacement dynamics in a pore-throat network model.
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DOI：
10.1103/physreve.90.023019
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发表时间：
2014-08
期刊：
影响因子：
--
通讯作者：
F. Moebius;D. Or
中科院分区：
文献类型：
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作者：
F. Moebius;D. Or
多孔介质中流体驱替前沿在宏观尺度上看似规则和连续的运动是由许多（基本上不可见的）孔隙尺度的突然界面跳跃和压力爆发推动的。多孔介质中的流体前沿的特点是尖锐的相位不连续性和快速的孔隙尺度动力学的基础上，他们的运动，这两个属性挑战标准的连续理论，这些流动过程。此外，孔隙尺度动力学的细节影响前面的形态和随后的相截留后面的前面，从而形成关键的宏观输运性质的非饱和区。该研究提出了一个孔喉网络模型，重点是量化界面动态和相互作用沿着流体驱替前沿。多孔介质是由一个网格的连接孔喉能够滞留水，并引起流体-流体界面跳跃（研究重点是流量控制排水）。对于每个弯月面沿着的位移前，我们制定了一个本地的惯性，毛细管，粘性，和流体静力平衡，然后同时解决了整个前线。该模型能够系统地评估惯性和边界条件的作用。结果表明，而位移模式的影响，主要是由入侵的喉咙具有较高的毛细管阻力的惯性力，相截留（残余饱和度）在很大程度上是不受惯性，限制惯性影响的水文特性背后的一个阵线。界面跳跃速度通常比平均前沿速度大一个数量级，强烈依赖于几何喉道尺寸，并且当考虑惯性时变得更不可预测（更分散）。模型模拟的毛管压力波动和入侵事件之间的等待时间的分布遵循指数分布，并与实验结果吻合良好。该建模方法提供了深入了解位移前沿丰富的孔隙尺度动力学;这些见解不仅提高了对这些普遍存在的过程的基本理解，而且可以揭示前沿的溶质分散和胶体动员以及通过前沿的机械后果。
The seemingly regular and continuous motion of fluid displacement fronts in porous media at the macroscopic scale is propelled by numerous (largely invisible) pore-scale abrupt interfacial jumps and pressure bursts. Fluid fronts in porous media are characterized by sharp phase discontinuities and by rapid pore-scale dynamics that underlie their motion; both attributes challenge standard continuum theories of these flow processes. Moreover, details of pore-scale dynamics affect front morphology and subsequent phase entrapment behind a front and thereby shape key macroscopic transport properties of the unsaturated zone. The study presents a pore-throat network model that focuses on quantifying interfacial dynamics and interactions along fluid displacement fronts. The porous medium is represented by a lattice of connected pore throats capable of detaining menisci and giving rise to fluid-fluid interfacial jumps (the study focuses on flow rate controlled drainage). For each meniscus along the displacement front we formulate a local inertial, capillary, viscous, and hydrostatic force balance that is then solved simultaneously for the entire front. The model enables systematic evaluation of the role of inertia and boundary conditions. Results show that while displacement patterns are affected by inertial forces mainly by invasion of throats with higher capillary resistance, phase entrapment (residual saturation) is largely unaffected by inertia, limiting inertial effects on hydrological properties behind a front. Interfacial jump velocities are often an order of magnitude larger than mean front velocity, are strongly dependent on geometrical throat dimensions, and become less predictable (more scattered) when inertia is considered. Model simulations of the distributions of capillary pressure fluctuations and waiting times between invasion events follow an exponential distribution and are in good agreement with experimental results. The modeling approach provides insights into the rich pore-scale dynamics of displacement fronts; these insights not only improve the basic understanding of these ubiquitous processes, but could shed light on solute dispersion and colloids mobilization at fronts and the mechanical consequences of passing fronts.