Three-dimensional viscous fingering of miscible fluids in porous media
Three-dimensional viscous fingering of miscible fluids in porous media
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多孔介质中混溶流体的三维粘性指法
DOI：
10.1103/physrevfluids.2.103902
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发表时间：
2017
影响因子：
2.7
通讯作者：
Nagatsu Yuichiro
中科院分区：
文献类型：
--
作者：
Suekane Tetsuya;Ono Jei;Hyodo Akimitsu;Nagatsu Yuichiro
粘性指进是一种流动不稳定性，当较低粘性流体(LVF)驱替较粘性流体(MVF)时，在驱替前沿产生流动不稳定性。由于多孔介质的不透明性，对粘性指进结构及其随时间发展的实验研究大多局限于二维多孔介质或Hele-Shaw胞腔。在这项研究中，我们利用微聚焦X射线计算机层析成像(CT)扫描仪研究了多孔介质中粘性指进的三维特征。与二维实验类似，在三维粘性指进中也观察到了尖端分裂、屏蔽和合并等特征事件。在固定的粘度比下，随着Péclet数的增加，出现在界面上的手指趋于精细；但是，对于相同注入体积的LVF，手指尖端的位置保持不变。手指伸长与ln成正比增加，在初始界面出现的手指数目随ln增加。这一事实与线性稳定性分析定性一致。在手指内，X射线CT扫描仪所需的局部NaI浓度呈线性下降，而在指尖则急剧下降。局部较高的Péclet数以及在横向上的非定常运动可能会增强指尖的色散。随着粘度比的增大，各波及效率单调下降并趋于渐近状态；混合程度随粘度比的增大而增大。在高流量下，高粘度比下波及系数的渐近值较低，而与Péclet数的关系不明显。
Viscous fingering is a flow instability that is induced at the displacement front when a less-viscous fluid (LVF) displaces a more-viscous fluid (MVF). Because of the opaque nature of porous media, most experimental investigations of the structure of viscous fingering and its development in time have been limited to two-dimensional porous media or Hele–Shaw cells. In this study, we investigate the three-dimensional characteristics of viscous fingering in porous media using a microfocused x-ray computer tomography (CT) scanner. Similar to two-dimensional experiments, characteristic events such as tip-splitting, shielding, and coalescence were observed in three-dimensional viscous fingering as well. With an increase in the Péclet number at a fixed viscosity ratio,, the fingers appearing on the interface tend to be fine; however, the locations of the tips of the fingers remain the same for the same injected volume of the LVF. The finger extensions increase in proportion to ln, and the number of fingers emerging at the initial interface increases with. This fact agrees qualitatively with linear stability analyses. Within the fingers, the local concentration of NaI, which is needed for the x-ray CT scanner, linearly decreases, whereas it sharply decreases at the tips of the fingers. A locally high Péclet number as well as unsteady motions in lateral directions may enhance the dispersion at the tips of the fingers. As the viscosity ratio increases, the efficiency of each sweep monotonically decreases and reaches an asymptotic state; in addition, the degree of mixing increases with the viscosity ratio. For high flow rates, the asymptotic value of the sweep efficiency is low for high viscosity ratios, while there is no clear dependence of the asymptotic value on the Péclet number.