Spreading characteristics of an insoluble surfactant film on a thin liquid layer: comparison between theory and experiment
Spreading characteristics of an insoluble surfactant film on a thin liquid layer: comparison between theory and experiment
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DOI：
10.1017/s002211200500621x
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发表时间：
2005-12-10
影响因子：
3.7
通讯作者：
Troian, SM
中科院分区：
文献类型：
--
作者：
Dussaud, AD;Matar, OK;Troian, SM
我们描述了在稀薄的水性甘油混合物表面上铺展油酸膜期间表面斜率的测量和界面形状的重建。该实验系统密切模仿了不溶性表面活性剂膜在切向（马兰戈尼）表面应力的作用下在薄粘性层上铺展的行为。折射图像莫尔形貌用于监测宏观距离上表面坡度的演变，从中推断出随时间变化的界面形状和表面活性剂膜的前进速度。界面轮廓在表面活性剂源之前表现出强烈的表面凹陷，并在表面活性剂前缘处由升高的边缘覆盖。表面坡度和形状以及前进边缘的传播特性可以直接与理论预测进行比较。当模型允许初始液体层存在少量表面污染时，这种一致性非常强。理论和实验曲线之间的比较揭示了初始剪切应力在确定膜厚度和表面活性剂分布的演变中的重要性。这种初始应力似乎使下面的液体支撑变得如此剧烈，以至于表面活性剂液滴表现为有限源而不是无限源，即使在原点总是存在过量的表面活性剂。
We describe measurements of the surface slope and reconstruction of the interface shape during the spreading of an oleic acid film on the surface of a thin aqueous glycerol mixture. This experimental system closely mimics the behaviour of an insoluble surfactant film driven to spread on a thin viscous layer under the action of a tangential (Marangoni) surface stress. Refracted image Moire topography is used to monitor the evolution of the surface slope over macroscopic distances, from which the time variant interface shape and advancing speed of the surfactant film are inferred. The interfacial profile exhibits a strong surface depression ahead of the surfactant source capped by an elevated rim at the surfactant leading edge. The surface slope and shape as well as the propagation characteristics of the advancing rim can be compared directly with theoretical predictions. The agreement is quite strong when the model allows for a small level of pre-existing surface contamination of the initial liquid layer. Comparison between theoretical and experimental profiles reveals the importance of the initial shear stress in determining the evolution in the film thickness and surfactant distribution. This initial stress appears to thin the underlying liquid support so drastically that the surfactant droplet behaves as a finite and not an infinite source, even though there is always an excess of surfactant present at the origin.