On the Influence of Surfactants on the Wake and Shape of Gaseous Bubbles Ascending in Liquids

Industrial and natural two-phase flows of immiscible fluids with large density and viscosity ratios, such as ascending bubble flows, are impure. The shape and wake flow of ascending bubbles are a consequence of the interaction of gas and liquid at and with their common interface. At the interface, surfactants accumulate and affect its dynamic behavior. The dependence on the concentration and properties of the surfactant is, however, hard to study experimentally as well as numerically due to the lack of appropriate methods. We have developed a level-set based Eulerian sharp interface method for the numerical simulation of viscous, incompressible, immiscible two-phase flows. It accounts for viscous, capillary and Marangoni stresses directly at the interface and is fully conservative. The two latter depend on the local surfactant concentration, which is also modeled conservatively in Eulerian space. In this work, we employ this state of the art method to study the influence of surfactant parameters on the wake and shape of gaseous bubbles rising in liquid media. Besides investigating the bubble dynamics itself, we illuminate the dynamic redistribution of surfactant. As a consequence of our investigations, we give first guidelines for improving the controllability of bubble shape and wake by surfactant parameters. * We acknowledge the Deutsche Forschungsgemeinschaft (DFG) for funding. F.S.S. is member of the TUM Graduate School.     «

Industrial and natural two-phase flows of immiscible fluids with large density and viscosity ratios, such as ascending bubble flows, are impure. The shape and wake flow of ascending bubbles are a consequence of the interaction of gas and liquid at and with their common interface. At the interface, surfactants accumulate and affect its dynamic behavior. The dependence on the concentration and properties of the surfactant is, however, hard to study experimentally as well as numerically due to the...     »