Experimental investigation of the effects of surfactant on the dynamics of formation process of liquid drops

Abstract

In the present study, the formation of surfactant-laden viscous drops in ambient air is experimentally investigated using a high-speed digital camera. The mixtures of 90%, 92.5%, and 95% glycerol by weight in water containing various concentrations of sodium dodecyl sulfate are chosen as the drop phase fluid. The focus of this work is to investigate the effects of concentration of surfactant dissolved in solutions with different viscosities, on physical and geometrical parameters related to drop formation process, such as the drop elongation, minimum neck thickness, formation time, and the drop volume. The formation of satellite drops and the influence of surfactant concentration on their size are also studied. The obtained results indicate that increasing the surfactant concentration and the viscosity of drop phase fluid, slows down the necking process and causes the drop detachment length to increase. The entire process of drop formation is divided into two stages, and it was found that adding surfactant to the solutions has inverse effects on the duration of these two stages. It was also shown that surfactant addition contributes to an increase in the size of the satellite drop due to generation of Marangoni stresses on the surface of the drop's neck.