Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - DISFILM (Fluorescent-based innovative measure in thin liquid films: A way to understand stability and energy dissipation in foams and emulsions)

Teaser

Nobody knows why a soap bubble collapses. When the liquid film forming the bubble, stabilised by surfactants, becomes too thin, it collapses. This seemingly simple problem, ruled by the classical laws offluid mechanics and of statistical physics, is still a challenge for the...

Summary

Nobody knows why a soap bubble collapses. When the liquid film forming the bubble, stabilised by surfactants, becomes too thin, it collapses. This seemingly simple problem, ruled by the classical laws of
fluid mechanics and of statistical physics, is still a challenge for the physicist. The rupture criteria based on a stability analysis in the vicinity of the film equilibrium state fail to reproduce the observations. However the
film ruptures in a foam obey some simple phenomenological laws, which suggest that underlying fundamental laws exist and wait to be determined. The state-of-the-art conjecture is that ruptures are related
to hydrodynamical processes in the films.
Foams are widely used in industry and most of the stability issues have been solved. Nevertheless, most of the industrial formulations must
currently be modified in order to use green surfactants. This adaptation will be extremely more efficient and possible if the flows in the liquid part of the foam are understood.

Work performed

\"During the first period of the project, a deformable frame, called a \"\"thin film rheometer\"\", has be designed. It reproduces on few thin films the deformations occurring in a foam sample.
The link between forces and deformation is such system is now investigated.
A first success has been to quantify the mechanical influence of a film on its first neighbour, in a foam structure.\"

Final results

We aim to determine, on the basis of fundamental concepts, the expression of the foam apparent viscosity, and the dynamical path leading to its collapse.