Three-dimensional visualization of viscous fingering for non-Newtonian fluids with chemical reactions that change viscosity
Three-dimensional visualization of viscous fingering for non-Newtonian fluids with chemical reactions that change viscosity
复制标题
具有改变粘度的化学反应的非牛顿流体的粘性指法的三维可视化
DOI：
10.1103/physrevfluids.4.054502
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Anindityo Patmonoaji
中科院分区：
文献类型：
--
作者：
Sotheavuth Sin;Tetsuya Suekane;Yuichiro Nagatsu;Anindityo Patmonoaji
粘性指进（Viscous fingering，VF）是指在多孔介质中低粘性流体（LVL）取代高粘性流体（MVL）时发生的流体动力学流动不稳定性。在这项研究中，我们研究了VF的三维（3D）特性的可混溶的非牛顿流体与化学反应和不使用微焦点X射线计算机断层扫描仪。当体系的粘度随着化学反应而增加时，VF被抑制，并发生活塞式位移。置换LVL的圆柱形区域被高粘度膜状层包围，因为化学反应阻碍了LVL和MVL的混合。因此，该层内的高LVL浓度被保留而不与MVL混合。在LVL和MVL之间的界面处的粘度曲线中出现了明显的局部粘度峰。在峰值之后，出现了沿流动方向沿着增加粘度的不利粘度曲线，但由于平滑的粘度梯度，因此不会引起VF。在峰值之后，粘度曲线处于有利条件。在无反应的情况下，指尖比反应的情况下进一步前进，并且随着Pe的减小而进一步前进，这反映了剪切稀化流体的性质。相比之下，在具有化学反应的粘度降低的系统中，与没有反应的系统相比，手指的尖端位于更大的距离处。由于LVL和MVL的强烈混合，手指中的浓度从注射点开始急剧下降。结果，反应性病例中注射LVL的面积分数低于非反应性病例。指尖随着时间的推移而前进，而在反应性情况下，手指中的LVL浓度几乎没有恢复到0.4以上，这反映了强烈的指进和混合。
Viscous fingering (VF) is a hydrodynamic flow instability that occurs when a less-viscous liquid (LVL) displaces a more-viscous liquid (MVL) in porous media and takes place in either miscible or immiscible systems. In this study, we investigated the three-dimensional (3D) characteristics of VF for miscible non-Newtonian fluids with and without chemical reactions using a microfocus x-ray computed tomography scanner. When the viscosity of a system increased with a chemical reaction, the VF was suppressed, and pistonlike displacement occurred. The cylindrical domain of displacing LVL was surrounded by a high-viscosity filmlike layer because of the chemical reaction that impeded the mixing of the LVL and MVL. Consequently, the high LVL concentration inside this layer was retained without mixing with the MVL. A clear local peak in viscosity appeared in the viscosity profiles at the interface between the LVL and MVL. Behind the peak, an unfavorable viscosity profile of increasing viscosity along the flow direction appeared, but the VF was not induced because of the smooth viscosity gradients. After the peak, the viscosity profiles were in favorable conditions. In the nonreactive case, the tip of the fingers further advanced compared with that in the reactive case and went further with the decrease in Pe, which reflected the property of shear-thinning fluids. By contrast, in a decreasing-viscosity system with a chemical reaction, the tips of the fingers were located at a larger distance compared with that without reaction. The concentration in the finger intensively decreased from the point of injection because of the intensive mixing of the LVL and MVL. As a result, the area fraction of injected LVL in the reactive cases was lower than that in the nonreactive cases. The tip of the finger advanced with time, whereas LVL concentration in the finger hardly recovered above 0.4 in the reactive case, which reflected intensive fingering and mixing.