Marginal regeneration is the main thinning mechanism of a mobile vertical free liquid film, whereby thicker film regions, including the surfaces, are sucked in by the Plateau border, in exchange for thinner regions in an immediately adjacent section. Its hydrodynamic theory is confirmed by calculations performed on profiles of films, drawn from a 0.02 M CTAB solution, where the net flow out of the film is described as a result of a surface flow combined with a bulk flow caused by a pressure gradient.
The effect of hydrophilic glass particles in a cetyltrimethylammonium bromide (CTAB) solution on the drainage and stability of foam and single vertical free liquid films (0.02 M CTAB) in a glass frame was investigated. Large particles (diameter approximately between 1 and 10 ~m), being present in the colored films, retard both foam and film drainage and increase film stability. This is ascribed to dispersion of surface waves by particles extending through the film surfaces. Smaller particles (<1 ~tm) lack this property: they shorten film lifetime in foams, although they have no influence on foam drainage.
Profiles of the Plateau border at a vertical film in a 0.02 M cetyltrimethylammonium bromide solution are measured by optical interference, in the part of the border near the film, at two heights above the bulk liquid surface. The Laplace pressure in the border, calculated from these profiles, appears to be lower than the hydrostatic equilibrium pressure at a height close to the bulk liquid meniscus (6.2 mm); at a greater altitude ( 11.3 mm) the pressures are equal. An upward flow in the border close to the film is observed, while a downward flow takes place in the periphery of the border. Both effects can be explained by Marangoni flows. 0
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