Gas‐liquid flow in microchannels is relevant to a number of microfluidic devices without moving parts for application in chemical micro‐processing, inkjet printing, and electronics cooling. Over a large range of gas and liquid flow rates, gas bubbles have the same size as that of the channel. Such bubbles are nearly spherical in shape until their radius is less than that of the channel. The bubbles with a larger volume expand along the axis taking a capsular or bullet shape and are commonly known as Taylor bubbles. For air‐water flow, the spherical bubble is observed to move with a velocity higher than that of the Taylor bubble. In this work, the flow of a Taylor bubble followed by a spherical one, initially separated by several channel diameters, has been studied numerically using the volume of fluid (VOF) method. The hydrodynamics during the bubble approach as well as the evolution of the doublet, that is, the merged bubble, has been investigated. To track the velocity of each bubble with time during the bubble approach stage, a novel methodology has been developed using k‐means clustering algorithm. The evolution of the interface of the doublet has been monitored. The neck radius of the doublet grows as τ^0.5, τ being the time since the contact between the bubble interfaces, when the interface is away from the wall. In the near wall region, the radius grows more slowly and is proportional to τ^0.1.

中文翻译：

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微通道中气泡聚结的流体力学

微通道中的气液流动与许多微流体设备有关，这些微流体设备没有用于化学微处理，喷墨印刷和电子冷却的移动部件。在较大的气体和液体流速范围内，气泡的大小与通道的大小相同。这些气泡的形状几乎是球形的，直到它们的半径小于通道的半径为止。具有较大体积的气泡沿囊或子弹形状的轴扩展，通常称为泰勒气泡。对于空气水流，观察到球形气泡以比泰勒气泡更高的速度运动。在这项工作中，已经使用流体体积（VOF）方法在数值上研究了泰勒气泡的流动，然后是球形气泡的流动，最初是由几个通道直径分开的。已经研究了气泡接近过程中的流体动力学以及双峰（即合并气泡）的演化。为了在气泡逼近阶段随时间跟踪每个气泡的速度，已经开发了一种使用k均值聚类算法的新颖方法。双重结构的界面的演变已受到监测。双峰的颈部半径随着τ ^0.5， τ是由于气泡界面之间的接触，当所述接口是远离墙壁的时间。在近壁区，半径生长更慢，正比于τ ^0.1。