Expérimental et théorique
Processes involving liquids often face unwanted foaming issues (eg lubrication), while foaming is instead desired when intimate mixing of gas and liquid phases is needed (eg. chemical reaction with O2). Hence, controlling the bubble lifetime is crucial to applications. Extensive studies have been conducted on aqueous foams stabilized by surfactants, and have unveiled intricate mechanisms due to molecular adsorption of surfactants at the air/liquid interface. Recently, foaming of liquid mixtures has emerged as a model system to isolate some of the physical mechanisms ensuring bubble stability. Indeed, interfacial effects due to evaporation can be minimized, delays in interfacial adsorption are suppressed, thereby reducing the couplings between bulk and interface transfers. In addition, foaming of liquid mixtures is relevant to a large number of practical situation in which foams exist without adding surfactants. The internship aims at further describing the physical mechanisms acting to stabilize foams of two mixed liquids [1]. To do so, we will perform experiments to quantitatively relate the lifetime of a bubble in a macroscopic column of foam (Fig A) to that of a single suspended liquid film (Fig B). We will particularly explore the effects of the bubble radius which sets the curvature and hence the capillary pressure gradients. These experiments will be analyzed and interpreted to improve our understanding of the stabilizing mechanisms in oil foams.