Effects of surfactants on the retraction dynamics of a freely suspended viscous liquid sheet*

In diverse applications including atomization and polymer processing, liquid sheets (liquid films with two free surfaces) are ejected from nozzles or dies. The cross-sections of sheets are virtually rectangular in shape but have rounded ends which contract or retract towards each other due to surface tension forces. Commonly, liquid sheets ejected from agricultural spray nozzles also have surfactants present at the air-liquid interface either by design or as contaminants. Previous studies have shown that surfactants drastically change the dynamics of planar films and filaments by either affecting the breakup dynamics or causing escape from end pinching (Wee et al., Phys. Rev. Fluids, 2022; Kamat et al., JFM, 2020). In this talk, we will report the results of a study investigating the effect of surfactants on the contraction dynamics of liquid sheets and extend the previous works of others on systems with clean interfaces (Notz and Basaran, JFM, 2004; Savva and Bush, JFM, 2009).