title: Influence of surfactants on the force between two bubbles.
abstract: The retardation of the interfacial velocity due to the presence of surface-active species is a key feature that determines the magnitude of the dynamic interaction force between colliding bubbles. Here we derive simple measures to quantify the influence of a surface-active species during a head-on collision between bubbles to be used as guidelines in the design and analysis of emulsion stability and related experiments. These measures are derived from a theoretical model that was found to be consistent with experiment and are shown to characterize the interfacial dynamics without the need to use numerical analysis. It is shown that a surface mobility may change with the geometry of the film between the bubbles for a specific amount of a surface-active species. However, small amounts of surface-active species are sufficient to immobilize the interfaces under most physical conditions as found in earlier studies.
authors.affiliation: Particulate Fluids Processing Centre, Department of Mathematics and Statistics, The University of Melbourne, Parkville, Victoria 3010, Australia. O.Manor@ms.unimelb.edu.au
authors.forename: Ofer
authors.initials: O
authors.lastname: Manor
authors.forename: Derek Y C
authors.initials: DY
authors.lastname: Chan