Laboratoire Matière et Systèmes Complexes

MSC : Pierre Rognon (post-doc 2007-2008), Cyprien Gay, Marc Durand, Francois Graner

Collaborations : Howard Stone (Princeton), Sylvain Bénito, Charles-Henri Bruneau, Thierry Colin (Bordeaux), Doug Reinelt (SMU, Dallas, Texas, USA), François Molino (Montpellier).

Foams are complex materials because they are made of contacting, deformable elements (the bubbles). Mysteries remain in the dynamics of the bubbles. In our Laboratory, we study fast foam dynamics and lower frequency dynamics, called rheology.

A foam is a solid since it does not flow (if we except coalescence, coarsening or drainage). But it is a plastic solid whose threshold corresponds to large deformations. We are interested in several questions dealing with its rheology.

 On the local scale, when foam is flowing, bubbles are sliding over each other. We study the dynamics of the elementary relaxation process (T1 change) associated with the local exchange of neighboring bubbles [1].

 On the macroscopic scale, we have elaborated a continuous rheological model that takes these threshold and flow properties into account [2,5].

 Another macroscopic property is that the foam dilates slightly when deformed, like a granular material. We address the physical origin of this dilatancy in the case of foams [3,4].

 [1] M. Durand and H. A. Stone, “Relaxation time of the topological T1 process in a two-dimensional foam”, Phys. Rev. Lett. 97 226101 (2006)

 [2] S. Bénito, C.-H. Bruneau, T. Colin, C. Gay, F. Molino, ”An elasto-visco-plastic model for immortal foams or emulsions”, Eur. Phys. J. E 25 225-­251 (2008)

 [3] Pierre Rognon, François Molino, Cyprien Gay, "Prediction of positive and negative elastic dilatancy in 2D and 3D liquid foams", EPL 90(3) 38001 (2010)

 [4] Cyprien Gay, Pierre Rognon, Doug Reinelt, François Molino, "Rapid Plateau border size variations expected in three simple experiments on 2D liquid foams", Eur. Phys. J. E 34 1-11 (2011).

 [5] Sylvain Bénito, François Molino, Charles-Henri Bruneau, Thierry Colin, Cyprien Gay, "Non-linear oscillatory rheological properties of a generic continuum foam model: comparison with experiments and shear-banding predictions", Eur. Phys. J. E 35 51 (2012).