Abstract: 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.

Key words: soluble surfactant, Marangoni effect, positive system, negative system, stability