Column and film lifetimes in bubble-induced two-liquid flow

Abstract

We investigated the transient behavior of immiscible two-liquid interfaces initiated by a single rising gas bubble and characterized by liquid "column" and "film" morphologies. To analyze the effect of the buoyancy force, viscosity, and interfacial tension on these morphologies, the single-solution density was controlled continuously by association with the rising velocity of the bubble. It was observed that the extension of the liquid column further into the upper liquid phase owing to the wake flow under the bubble is driven by the buoyancy force, with the velocity decreasing gradually with the distance between the bubble and the liquid-liquid interface. Based on this mechanism, we determined that a strong dimensionless correlation exists between the lifetime of the column and the physical properties of the two liquid phases. On the other hand, gravitational drainage does not affect the film lifetime. However, marginal pinching is dominant, probably owing to the existence of a surface tension gradient between the film and the meniscus.

Lifetime of Surface Bubbles in Surfactant Solutions

“…Finally, we observed that the bubble deformation, Marangoni stresses, and associated longer lifetime of bubbles are related to a necking phenomena in the thin film (inversion of curvature). The apparition of this neck could be the precursor of a 3D instability at the origin of marginal regeneration. ,, Bridging the gap between the necking phenomena and the longer bubble lifetime as well as identifying the influence of surfactant type (for instance, via the minimum surface tension parameter σ ∞ /σ 0 ) is an open route for future investigations.…”

“…The apparition of this neck could be the precursor of a 3D instability at the origin of marginal regeneration. 6,26,28 Bridging the gap between the necking phenomena and the longer bubble lifetime as well as identifying the influence of surfactant type (for instance, via the minimum surface tension parameter σ ∞ /σ 0 ) is an open route for future investigations.…”

“…The onset of a dimple was shown to be governed by the variation of the curvature of the film over a small distance away from the bubble apex [23], and its further development was shown to depend upon the ratio of the film curvature at the bubble apex to the curvature near the rim region [24] and to the film thickness [25]; all these factors depend on the bubble rising velocity, on its shape and on surfactant distribution at the thin film interfaces. Finally, the formation of a dimple is often associated, at later stages of the drainage, to the breakage of axisymmetry in the film thickness distribution and eventually to the marginal regeneration phenomenon [26], [18], [6], [27], [28]. Based on the drainage laws summarized above, one retains that only the pure viscousgravity drainage with stress-free interfaces for large bubbles gives an exponential decay (Eq.…”

“…All of these factors depend on the bubble rising velocity, on its shape, and on the surfactant distribution at the thin film interfaces. Finally, the formation of a dimple is often associated, at later stages of the drainage, to the breakage of axisymmetry in the film thickness distribution and eventually to the marginal regeneration phenomenon. ,,− …”

Spontaneous colloidal metal network formation driven by molten salt electrolysis

“…water-oil. Also, because it is a very unstable interface, interfacial tension gradient can easily occur there (Appendix 2) 55,56 . For the flow generated at the liquid Me-molten salt interface, the mechanism discussed above is schematically shown in Fig.…”