Coalescence of a millimeter-sized drop initially touching a pool of the same liquid in the presence of another surrounding viscous liquid is studied in this work, wherein the drop may be hotter or colder than its surroundings. Moreover, the effect of the outer fluid viscosity on the coalescence dynamics and thermal convection is examined. An axisymmetric numerical model is employed to investigate the drop merger dynamics, wherein the drop and pool are modeled as water fluid, and the surroundings are modeled as silicone oils of different viscosities. The coalescence behaviors of hot and cold drops are found to be significantly different, especially at higher temperature differences. An otherwise partial coalescence for an isothermal system turns into a case of total coalescence when the drop is made colder than its surroundings, whereas the behavior in the case of a hot drop does not depart qualitatively from that of a corresponding isothermal system. Thermal convection has been examined in terms of the penetration depth of hot or cold fluid into the pool. Hot drops are found to have a greater penetration depth as compared to cold drops for higher viscosities of the surrounding fluid. The penetration depth is also related to the size of the leading vortex ring and the maximum vorticity magnitude.

中文翻译：

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在周围粘性液体存在的情况下，热滴和冷滴的不同聚结行为

在这项工作中，研究了在存在另一种周围粘性液体的情况下最初接触同一液体池的毫米大小的液滴的聚结，其中液滴可能比周围环境更热或更冷。此外，检查了外部流体粘度对聚结动力学和热对流的影响。采用轴对称数值模型研究液滴合并动力学，其中液滴和水池被建模为水流体，周围环境被建模为不同粘度的硅油。发现热滴和冷滴的聚结行为显着不同，尤其是在较高的温差下。当液滴比周围环境更冷时，等温系统的其他部分聚结变成完全聚结的情况，而在热滴情况下的行为与相应的等温系统的行为在性质上没有区别。热对流已根据热流体或冷流体进入水池的渗透深度进行了检查。发现与周围流体粘度较高的冷滴相比，热滴具有更大的穿透深度。穿透深度还与前导涡环的大小和最大涡量大小有关。