Bursting of rigid bubbles

We propose here a fluid dynamics video relating the bursting of soap rigid films.Comment: 4 pages and 2 videos included for the Gallery of Fluid Motion 201

Holes and cracks in rigid foam films

The classical problem of foam film rupture dynamics has been investigated when surfaces exhibit very high rigidity due to the presence of specific surfactants. Two new features are reported. First a strong deviation to the well-known Taylor-Culick law is observed. Then, crack-like patterns can be visualized in the film; these patterns are shown to appear at a well defined deformation. The key role of surface active material on these features is quantitatively investigated, pointing the importance of surface elasticity to describe these fast dynamical processes, and thus providing an alternative tool to characterize surface elasticity in conditions extremely far from equilibrium. The origin of the cracks and their consequences on film rupturing dynamics are also discussed

Films de savons rigides : dynamique de rupture

L’éclatement d’un film de savon, dont les premières études remontent au début du XXe siècle, est généralement décrit par la compétition entre l’inertie du liquide mis en mouvement et la tension de surface d’équilibre, responsable de l’ouverture du trou [1, 2, 3]. D’un autre côté, dans les films de savon ou les mousses, qui sont des assemblées de films, plusieurs phénomènes dynamiques comme le drainage [4] ou la rhéologie [5] dépendent de façon cruciale de la nature des molécules tensioactives, qui peuvent rigidifier les interfaces liquide-gaz. Nous étudions ici l’éclatement d’un film de liquide contenant un mélange de tensioactifs réputé pour sa grande élasticité inter faciale [6]. Dans ce cas, nous montrons que les tensioactifs sont responsables d’un ralentissement de la dynamique d’ouverture par rapport à la loi classique de Taylor-Culick. Cette dynamique est pilotée par la compétition entre l’inertie et l’élasticité de surface que nous contrôlons. De façon similaire à ce que l’on observe pour une membrane élastique solide, pour de grandes compressions, la rigidité des interfaces conduit à la formation de motifs localisés, comparables à des plis ou des fractures. Nous montrons que l’apparition de ces motifs s’accompagne d’une modification de la dynamique d’ouverture

Computational study of the role of surfactants in sheared foams for foam stability

The dynamics of sheared wet foams is investigated computationally in this study. For this purpose, an established 3D (parallel) implementation of a level-set method for incompressible two-phase flow has been extended to account for the presence of surfactants that are soluble in the liquid, and the associated modified stress conditions at interfaces. In particular, we account for surface rheological behavior (such as surface viscosity) beyond minimal surfactant models, to describe realistic systems. The results of 2D and 3D tests will be demonstrated to compare favourably with the literature. We shall report on the role of surfactants and their properties on T1 events, wherein adjacent bubbles are sheared past each other, with implications for foam instability

Thermodynamic and Mechanical Timescales Involved in Foam Film Rupture and Liquid Foam Coalescence

International audienc

Gouttes inertielles (de la caléfaction à l'étalement)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Thermally Enhanced Electro-osmosis to Control Foam Stability

Liquid foam is a dense dispersion of liquid bubbles in a surfactant solution. Because of its large surface area, it is an out-of-equilibrium material that evolves with space and time because of coarsening, coalescence, and liquid drainage. In many applications, it is required to control the lifetime of a foam by limiting the drainage or triggering the collapse at a specific location or a given time. We show here that applying an external electric field at the edge of the foam induces some liquid flows. Depending on the flow magnitude, it controls either gravity driven drainage, the foam stability, or the foam collapse at a specific location. Thus, applying an electric field to a liquid foam can control its stability. The experimental results are quantitatively described by a simple model taking into account first the electro-osmotic transport in such a deformable medium and second the Marangoni flows induced by heterogeneous heating due to Joule effect. More specifically, we show for the first time that electro-osmosis can be strongly enhanced due to thermal gradients generated by the applied electric field