Lamellae lifetime

The hybrid model has its lower and upper applicability limits for Weber and Re3molds numbers. It has a lower limit because the colhsion dynamics must be represented in a phase when a lamella is observed. If the lamella lifetime is too short, the model is not suitable. It has an upper limit because the evolution of the lamella thickness changes with increasing colhsion energy. The determination of... 

In pure liquids, gas bubbles will rise up and separate, more or less according to Stokes law. When two or more bubbles come together coalescence occurs very rapidly, without detectable flattening of the interface between them, i.e., there is no thin-film persistence. It is the adsorption of surfactant, at the gas-liquid interface, that promotes thin-film stability between the bubbles and lends a certain persistence to the foam structure. Here, when two bubbles of gas approach, the liquid film thins down to a persistent lamella instead of rupturing at the point of closest approach. In carefully controlled environments, it has been possible to make surfactant-stabilized, static, bubbles, and films with lifetimes on the order of months to years [45],... 

Wet foams in which the liquid lamellae have thicknesses on the same scale or larger than the bubble sizes. Typically in these cases the gas bubbles have spherical rather than polyhedral shape. Other synonyms include gas dispersion and kugelschaum . If the bubbles are very small and have a significant lifetime, the term microfoam is sometimes used. In petroleum production the term is used to specify crude oil that contains a small volume fraction of dispersed gas. See also Foam. 

The formation of ordered microstructure in thin liquid films offers a new mechanism for the stabilization of foams. As a proof of microstructuring in real foams, Figure 17 shows a photograph of an aqueous foam system stabilized because of the stratification in the foam bubble lamellae. The practical importance of the film microstructuring is that the lifetimes of foams with stratifying films are much longer. 

The result is a finite lifetime of lamellaes or foam bubbles respectively. 

Figure 13.7 Stages in a foam lifetime, (a) Spherical foam (independent gets bubbles), (b) gravity drainage period, (c) lamella thinning period and (d) film rupture. Berg (2010). Reproduced with permission from World Scientific...

The lifetimes Tc, tl, te, and tal characterize the macroscopic stress fatigue, the nanoscopic long period fatigue, the nanoscopic lamella-extension fatigue, and the nanoscopic structure-heterogeneity fatigue, respectively. Data in brackets are only based on a part of the curve (cf. Fig. 5.19)... 

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