Experimental study of entrainment and drainage flows in microscale soap films.
Experimental study of entrainment and drainage flows in microscale soap films.
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微型皂膜中夹带和排水流动的实验研究。
DOI：
10.1021/la047178
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
S. Troian
中科院分区：
文献类型：
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作者：
S. Berg;Eric A. Adelizzi;S. Troian
用激光反射率法研究了垂直抽放过程中自由悬浮表面活性剂膜的厚度。当毛细管数低于10（-3）时，提取过程产生的初始膜厚度在微米范围内；随后的变薄主要是由毛细管力而不是重力推动的。在这些条件下，我们的研究结果表明，在临界胶束浓度（cmc）以上和以下的薄膜变薄可以用一个幂律函数很好地近似，该函数的指数范围为-0.9至-1.8，与目前对不可扩展薄膜中毛细管粘性排水的描述不一致，该描述预测的指数接近-0.5。实验拟合参数之间的相关性说明了跨cmc的膜行为的重要差异。此外，对排水数据进行标准化处理后，在30多年的时间里，对于大范围的初始回采率，排水数据会崩溃为单一的功能形式。我们证明了通过有效滑移参数修正现有模型中的界面边界条件来考虑马兰戈尼应力，从而得到指数和其他关键参数的值，与实验结果非常吻合。这一改进也成功地描述了低于cmc的提取厚度。
The thickness of freely suspended surfactant films during vertical withdrawal and drainage is investigated using laser reflectivity. The withdrawal process conducted at capillary numbers below 10(-3) generates initial film thicknesses in the micrometer range; subsequent thinning is predominantly impelled by capillary and not gravitational forces. Under these conditions, our results show that film thinning above and below the critical micelle concentration (cmc) is well approximated by a power law function in time whose exponents, which range from -0.9 to -1.8, are inconsistent with current descriptions of capillary-viscous drainage in inextensible films which predict exponents close to -0.5. Correlations between the experimental fitting parameters illustrate important differences in film behavior across the cmc. In addition, normalization of the drainage data yields a collapse to a single functional form over 3 decades in time for a wide range of initial withdrawal rates. We demonstrate that modification of the interface boundary condition in current models to account for Marangoni stresses through an effective slip parameter yields values of the exponents and other key parameters in excellent agreement with experiment. This modification also successfully describes the withdrawal thickness below the cmc.