Esmaeilzadeh Soheil, Qin Zhipeng, Riaz Amir, Tchelepi Hamdi A
Department of Energy Resources Engineering, Stanford University, California 94305, USA.
Department of Geophysics, Stanford University, California 94305, USA.
Phys Rev E. 2020 Aug;102(2-1):023109. doi: 10.1103/PhysRevE.102.023109.
We study the interfacial evolution of immiscible two-phase flow within a capillary tube in the partial wetting regime using direct numerical simulation. We investigate the flow patterns resulting from the displacement of a more viscous fluid by a less viscous one under a wide range of wettability conditions. We find that beyond a wettability dependent critical capillary number, a uniform displacement by a less viscous fluid can transition into a growing finger that eventually breaks up into discrete blobs by a series of pinch-off events for both wetting and nonwetting contact angles. This study validates previous experimental observations of pinch-off for wetting contact angles and extends those to nonwetting contact angles. We find that the blob length increases with the capillary number. We observe that the time between consecutive pinch-off events decreases with the capillary number and is greater for more wetting conditions in the displaced phase. We further show that the blob separation distance as a function of the difference between the inlet velocity and the contact line speed collapses into two monotonically decreasing curves for wetting and nonwetting contact angles. For the phase separation in the form of pinch-off, this work provides a quantitative study of the emerging length and timescales and their dependence on the wettability conditions, capillary effects, and viscous forces.
我们使用直接数值模拟研究了部分润湿状态下毛细管内不混溶两相流的界面演化。我们研究了在广泛的润湿性条件下，低粘度流体驱替高粘度流体所产生的流动模式。我们发现，超过一个与润湿性相关的临界毛细管数后，对于润湿和非润湿接触角，低粘度流体的均匀驱替会转变为一个不断增长的指状物，该指状物最终会通过一系列颈缩事件分裂成离散的液滴。本研究验证了先前关于润湿接触角颈缩的实验观察结果，并将其扩展到非润湿接触角。我们发现液滴长度随毛细管数增加。我们观察到连续颈缩事件之间的时间随毛细管数减少，并且在被驱替相中润湿性更强的条件下更长。我们进一步表明，液滴分离距离作为入口速度与接触线速度之差的函数，对于润湿和非润湿接触角会汇聚成两条单调递减的曲线。对于以颈缩形式的相分离，这项工作对出现的长度和时间尺度及其对润湿性条件、毛细管效应和粘性力的依赖性进行了定量研究。
