Influence of surfactant concentration on drop production by bubble bursting

Abstract

Bubble bursting at the surface of the sea water produce drops and is the main source of sea spay aerosol. The mechanisms underlying the drops production from a single bubble bursting event have been intensively studied and the influence of the bubble size and liquid parameters (density, viscosity and surface tension) has been unified. However, despite the diversity of the surfactant molecules present in the oceans, their influence has been overlooked. In this paper we experimentally explore the influence of the surfactant concentration (Sodium Dodecyl Surfate - SDS) in a water solution on a single bubble collapse and subsequent drop production. We show that these surfactant molecules have an astonishing effect. In particular, we quantitatively show that they modify the bubble collapse, they induce less, smaller and faster drops and they can even completely prevent the drop production for a particular concentration. These results are presented in the existing dimensionless framework and they allow us to affirme that these effects are mainly a consequence of the surface tension gradients (Marangoni stresses) more than just the surface tension lowering. Finally, this study shows that the role of water contamination by surface-active agents is important and needs to be understood to improve the prediction of the sea spray aerosol.