Lin CK, Hwang CC, Uen WY
Department of Mechanical Engineering, Ching Yun Institute of Technology, Chung-Li, Taiwan, 32020, Republic of China
J Colloid Interface Sci. 2000 Nov 15;231(2):379-393. doi: 10.1006/jcis.2000.7155.
The effects of soluble surfactant on the dynamic rupture of thin liquid films are investigated. A nonlinear coupling evolution equation is used to simulate the motion of thin liquid films on free surfaces. A generalized Frumkin model is adopted to simulate the adsorption/desorption kinetics of the soluble surfactant between the surface and the bulk phases. Numerical simulation results show that the liquid film system with soluble surfactant is more unstable than that with insoluble surfactant. Moreover, a generalized Frumkin model is substituted for the Langmuir model to predict the instability of liquid film with soluble surfactant. A numerical calculation using the generalized Frumkin model shows that the surfactant solubility increases as the values of parameters of absorption/desorption rate constant (J), activation energy desorption (nu(d)), and bulk diffusion constant (D(1)) increase, which consequently causes the film system to become unstable. The surfactant solubility decreases as the rate of equilibrium (lambda) and interaction among molecules (K) are increased, which therefore stabilizes the film system. On the other hand, an increase of relative surface concentration (the index of a power law), beta(n), will initially result in a decrease of corresponding shear drag force as beta and n increase from 0 to 0.3 and 0.85, respectively. This will enhance the Marangoni effect. However, a further increase of beta and n to greater than 0.3 and 0.85, respectively, will conversely result in an increase of the corresponding shear drag force. This will weaken the Marangoni effect and thus result in a reduction of interfacial stability. Copyright 2000 Academic Press.
研究了可溶性表面活性剂对薄液膜动态破裂的影响。使用非线性耦合演化方程来模拟自由表面上薄液膜的运动。采用广义弗鲁姆金模型来模拟可溶性表面活性剂在表面相和本体相之间的吸附/解吸动力学。数值模拟结果表明，含有可溶性表面活性剂的液膜系统比含有不溶性表面活性剂的液膜系统更不稳定。此外，用广义弗鲁姆金模型替代朗缪尔模型来预测含有可溶性表面活性剂的液膜的不稳定性。使用广义弗鲁姆金模型的数值计算表明，随着吸附/解吸速率常数（J）、解吸活化能（nu(d)）和本体扩散常数（D(1)）的参数值增加，表面活性剂溶解度增加，这进而导致膜系统变得不稳定。随着平衡速率（lambda）和分子间相互作用（K）增加，表面活性剂溶解度降低，从而使膜系统稳定。另一方面，相对表面浓度（幂律指数）beta(n)增加时，当beta和n分别从0增加到0.3和0.85时，相应的剪切阻力最初会降低。这将增强马兰戈尼效应。然而，当beta和n分别进一步增加到大于0.3和0.85时，相应的剪切阻力会相反地增加。这将削弱马兰戈尼效应，从而导致界面稳定性降低。版权所有2000年学术出版社。
