Inter-bubble gas diffusion in liquid foam

Ostwald ripening (disproportionation) of gas–liquid foam is a process in which large bubbles grow at the expense of small bubbles because pressure differences drive inter-bubble gas diffusion. The rather overlooked theory of Robert Lemlich, for relatively wet foam, is revisited and its analogy with Ostwald ripening of metals grains discussed and this is put into context with recent advances. Lemlich's Theory assumes that the rate of disproportionation is governed by gas mass transfer, whereas recent work has suggested that it may be mechanically resisted by contraction/expansion of gas–liquid interfaces. In addition, the exact generalisation of the von Neumann Theory of grain growth to three dimensions is made quantitatively relevant to dry foams. Developments in tomographies and other experimental techniques have the potential to enable this model to be verified.

Graphical AbstractOstwald ripening of gas-liquid foam is a process in which large bubbles grow at theexpense of small bubbles because pressure differences drive inter-bubble gasdiffusion. The study of this process has attracted researchers from a number ofdisciplines, and a comprehensive survey of all this literature is without the scope ofthe present work. Instead, the rather overlooked theory of Robert Lemlich, forrelatively wet foam, is revisited and its analogy with Ostwald ripening of metalsgrains discussed. In addition, the exact generalisation of the von Neumann theory ofgrain growth to three-dimensions is made quantitatively relevant to dry foams. Recentadvances in tomographies and other experimental techniques have the potential toenable this model to be verified. Figure optionsDownload high-quality image (1499 K)Download as PowerPoint slide