Effect of surfactant redistribution on the flow and stability of foam films
Effect of surfactant redistribution on the flow and stability of foam films
复制标题
表面活性剂再分布对泡沫膜流动性和稳定性的影响
DOI：
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
R. Rosario
中科院分区：
文献类型：
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作者：
D. Vitasari;S. Cox;P. Grassia;R. Rosario
二维（2D）耗散泡沫流变学的粘性泡沫模型结合Marangoni驱动的表面活性剂在泡沫膜上的再分布。该模型是用来研究一个二维泡沫系统的流动，包括一个气泡部分填充一个狭窄的通道和一个单一的跨膜连接到对面的通道壁。由膜变形引起的表面张力的梯度引起沿膜沿着重新分布表面活性剂的切向流动。这种重新分布，以及随之而来的膜张力的变化，抑制了结构经历泡沫破坏拓扑变化，其中跨越膜留下气泡;泡沫稳定性由此增加。该系统的行为被归类为吉布斯-马兰戈尼参数，表示在切向和正常方向的运动速率之间的比率。吉布斯-马兰戈尼参数的值越大，表面张力的变化越大，表面活性剂再分布的速率越高，拓扑结构变化的可能性越小。然而，一个中间制度，其中的吉布斯-马兰戈尼参数是足够大的表面张力的显着梯度，但不足以完全平滑的流动引起的表面活性剂的重新分配，导致在非单调变化的气泡高度，因此在泡沫稳定性。
The viscous froth model for two-dimensional (2D) dissipative foam rheology is combined with Marangoni-driven surfactant redistribution on a foam film. The model is used to study the flow of a 2D foam system consisting of one bubble partially filling a constricted channel and a single spanning film connecting it to the opposite channel wall. Gradients of surface tension arising from film deformation induce tangential flow that redistributes surfactant along the film. This redistribution, and the consequent changes in film tension, inhibit the structure from undergoing a foam-destroying topological change in which the spanning film leaves the bubble behind; foam stability is thereby increased. The system’s behaviour is categorized by a Gibbs–Marangoni parameter, representing the ratio between the rate of motion in tangential and normal directions. Larger values of the Gibbs–Marangoni parameter induce greater variation in surface tension, increase the rate of surfactant redistribution and reduce the likelihood of topological changes. An intermediate regime is, however, identified in which the Gibbs–Marangoni parameter is large enough to create a significant gradient of surface tension but is not great enough to smooth out the flow-induced redistribution of surfactant entirely, resulting in non-monotonic variation in the bubble height, and hence in foam stability.