The motion of drops in water contaminated with a surface-active agent

Transient rise velocity and mass transfer of a single drop with interfacial instabilities – experimental investigations

“…The terminal and interfacial velocity is reduced if the liquid contains impurities or surfactants (e.g. Griffith, 1962;Edge and Grant, 1972;Levan and Newman, 1976;Hatanaka et al, 1988;Li et al, 2003). Some authors propose a stagnant cap model in order to describe the blockage effect of the interface through contaminants (e.g.…”

Numerical simulations of a rising drop with shape oscillations in the presence of surfactants

“…However, it is well known that only a residual amount of surfactant is sufficient to drastically change the droplet or bubble dynamics [1] compared to a case with clean interfaces. Indeed, the rising or settling velocity of a droplet was measured to be smaller [2,3] than the prediction of the Hadamard-Rybczynski theory for clean interfaces; this was explained for the first time by Frumkin and Levich [4] as a consequence of the flow caused at the interface by the existence of surface tension gradients, which is known as the Marangoni effect. Other consequences of the presence of surfactants can be observed in the drop or bubble dynamics, such as changes in the rising path regime [5], a noticeable decrease of heat and mass transfer rates between the continuous and the dispersed phase [6,7], and a prevention of drop coalescence [8].…”

Surface remobilization of buoyancy‐driven surfactant‐laden drops at low reynolds and capillary numbers

“…Follow‐up experimental studies observed shifts in the internal circulation and reductions in surface mobility . More quantitative studies followed such as by Edge and Grant using drops of dichloroethane settling in water containing sodium lauryl sulfate; Skelland et al using chlorobenzene drops settling in water containing anionic, cationic, and nonionic surfactants; and Bel Fdhila and Duineveld using air bubbles rising in water containing Triton X‐100. Malysa et al determined the concentration of surfactant necessary to affect bubble velocities rising in water containing n ‐butanol, α‐terpineol, and n ‐octanoic acid, while more recently Paul et al used settling drop velocities as a method for estimating the adsorption of sodium dodecyl sulfate (SDS) and Triton X‐100 surfactants on drop surfaces.…”