Hydrodynamics of thin liquid films. Effect of surfactants on the velocity of thinning of emulsion films

Film Drainage between Colliding Drops at Constant Approach Velocity: Experiments and Modeling

“…As a consequence, in these experiments, the viscosity of the drop phase has a negligible effect on the drainage behavior. This result is not surprising since it has previously been reported that only a small amount of surfactants is required to immobilize the interfaces (22)(23)(24). In the absence of mass transfer, drainage experiments with mobile interfaces need drastic conditions of liquid purity and equipment cleanliness.…”

“…∂ ∂r r ∂h ∂r [23] tangential stress balance τ d = − h 2 ∂p ∂r [24] coupling between interfacial velocity and interfacial viscous stress…”

Effect of Surfactants on the Film Drainage

“…[26b], [27], and [29], give simple analytical relationships for calculation of the drainage velocity. They predict a continuous transition from the deformed to the nondeformed bubbles approximation.…”

“…The corresponding models for emulsion films, for which the surfactant is soluble only in the continuous phase are described in Refs. 6,16,27,28. It was shown therein that in the presence of surfactants the energy dissipates mainly in the film region, and the emulsion films behave just as foam films.…”

Détermination expérimentale de l'efficacité de coalescence

“…Les modèles physiques des écoulements turbulents diphasiques permettent de prédire le cisaillement local responsable de la rencontre de deux globules, mais il faut ajouter un scalaire traduisant la probabilité de fusionnement (Mariaux [1990], Thomas [1981]). Cette probabilité peut être calculée par d'autres modèles physiques compliqués faisant appel aux propriétés des surfactants (Traykov et al [1977], 1vanov [1980], Zinchenko [1984], Muralidhar et al [1988], Danov et al [1994]), ou bien, et c'est la méthode que nous proposons, cette probabilité peut être déterminée expérimentalement pour une dispersion donnée.…”