不同液膜体系中Marangoni效应对活性剂液滴铺展的影响

针对含可溶性表面活性剂的液滴在预置液膜上的铺展过程,应用润滑理论建立液滴厚度、活性剂表面浓度及内部浓度演化过程的控制方程组,采用PDECOL程序模拟液滴的演化特征,探讨不同液膜体系下Marangoni效应的作用机理,并基于瞬态增长法分析负体系下液滴演化的不稳定性.研究表明,正体系下Marangoni效应可促进活性剂分子扩散,有利于活性剂液滴的稳定铺展;负体系下Marangoni效应则抑制液滴铺展,使液滴在中心区域产生振荡现象,呈现不稳定性特征,且该特征随负效应增强而愈加明显.在正负两种体系下,Marangoni作用力均是促使液滴横向演化的主要驱动力.

Marangoni Effect on Soluble Surfactant Droplet Spreading in Different Spreading Systems

Surfactant driven flows are simulated with three nonlinear partial differential evolution equations for film thickness, surfactant interracial and bulk concentrations based on lubrication theory via PDECOL program numerically, to investigate influence of Marangoni effect in positive, negative and neutral systems. Instability of droplet evolution in negative system is analyzed with method of transient growth analysis. It shows that Marangoni effect plays a positive role in promoting droplets non-uniform spreading and surfactant diffusion in a positive system. A system under negative Marangoni effect exhibits interfacial instability which resulted in spreading inhibited and violent fluctuations occurrence on droplet surface. Instability tends to be more obvious with strengthened effect. Marangoni stress is main driving force in transverse droplet evolution in both positive and negative systems.