An experimental study of the coalescence between a drop and an interface in Newtonian and polymeric liquids
An experimental study of the coalescence between a drop and an interface in Newtonian and polymeric liquids
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DOI：
10.1063/1.2349586
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发表时间：
2006-09-01
影响因子：
4.6
通讯作者：
Feng, James J.
中科院分区：
文献类型：
--
作者：
Chen, Xiaopeng;Mandre, Shreyas;Feng, James J.
当水滴落在油水界面上时，水滴通常会停留一段时间，然后才与界面下的水融合。我们报道了使用水和油基牛顿液体和聚合物溶液的实验，重点是非牛顿效应。我们推导出液滴表面被预先存在于流体中的污染物固定，并发现对于牛顿流体，停留时间与基质粘度成比例。将计算结果与油膜排液的润滑模型进行了比较。如果周围的基质是稀释的聚合物溶液，则休息时间与单独使用溶剂的基质的休息时间相同。进一步的研究表明，聚合物分子已经通过表面吸附从薄膜中被清除。根据流体性质和液滴大小的不同，液滴界面的合并可以一次完成，也可以通过部分合并的级联完成。对于中等大小的液滴，会发生部分聚结；对于较小的液滴，它会被粘度阻止；对于较大的液滴，它会被重力阻止。当液滴或基质相为聚合物溶液时，粘弹性对较小液滴的部分聚结有抑制作用。这显然是由于抑制了毛细管夹断，否则会在合并完成之前产生二次液滴。(C)2006年美国物理研究所。
When a water drop falls onto an oil-water interface, the drop usually rests for some time before merging with the water underneath the interface. We report experiments on this process using water- and oil-based Newtonian liquids and polymer solutions, with an emphasis on the non-Newtonian effects. We deduce that the drop surface is immobilized by contaminants pre-existing in the fluids, and find that the rest time scales with the matrix viscosity for Newtonian fluids. The results are compared with lubrication models for film drainage. If the surrounding matrix is a dilute polymer solution, the rest time is identical to that for a matrix of the solvent alone. Further investigation indicates that the polymer molecules have been cleared from the film by surface adsorption. Depending on the fluid properties and drop size, the drop-interface merging may be completed in one shot or through a cascade of partial coalescence. Partial coalescence occurs for an intermediate range of drop sizes; it is arrested by viscosity for smaller drops and by gravity for larger ones. When either the drop or the matrix phase is a polymer solution, viscoelasticity is shown to suppress partial coalescence for smaller drops. This is apparently due to the inhibition of capillary pinch-off which would otherwise produce a secondary drop before the merging is complete. (c) 2006 American Institute of Physics.