When two fluid drops touch, they coalesce due to surface tension. At early times, there is only a relatively small fluid bridge joining the drops. An asymptotic solution is presented for an inertial regime of early-time coalescence, in which inertial forces balance surface tension at leading order. It is demonstrated that viscosity nevertheless has a leading-order effect. Radial momentum is created at the tightly curved edge of the fluid bridge by the net force $2\gamma$ (per unit length) due to surface tension. This momentum is left behind the radially expanding bridge edge in a thin viscous wake. The divergent volume flux in the wake entrains fluid from above and below the bridge, and drives an inviscid irrotational flow in the drops on the scale of the bridge radius. This flow widens the gap between the drops ahead of the bridge, and the larger gap width results in a lower rate of coalescence. Including viscosity in this way improves the agreement between theory and the available experimental and numerical data.

中文翻译：

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具有一定粘度的液滴的惯性聚结

当两滴液体接触时，它们会由于表面张力而合并。早期，只有一个相对较小的液桥连接液滴。提出了早期聚结惯性状态的渐近解，其中惯性力在前导阶上平衡表面张力。事实证明，粘度仍然具有先导效应。净力在液桥紧密弯曲的边缘处产生径向动量 $2\伽玛$ （每单位长度）由于表面张力。这种动量以薄薄的粘性尾流的形式留在径向扩张的桥边缘后面。尾流中发散的体积通量夹带来自桥上方和下方的流体，并在桥半径范围内驱动液滴中的无粘性无旋转流。这种流动加宽了桥前方液滴之间的间隙，间隙宽度越大，聚结率越低。以这种方式包含粘度可以提高理论与可用实验和数值数据之间的一致性。