Life Time of Bubble rafts: Cooperativity and Avalanches

H. RITACCO; D. LANGEVIN

Golm, Potsdam. Germany

Conferencia; EuFoam 2006: European Conference on Foams, emulsions and Applications; 2006

Max Planck Institute of Colloids and Interfaces

We have studied the collapse of pseudo-bidimentional foams. These foams are formed of uniformly sized soap bubbles packed in an hexagonal lattice sitting at the top of a liquid surface. This corresponds to the limit of completely ordered wet foams with neither coarsening nor drainage.The collapse process can be divided in: (1) the collapse of the first bubble, driving by thermal fluctuations and (2) After the first bubble rupture, a cascade phenomena of bubble ruptures.We present a simple numerical model which captures the main characteristics of the dynamics of foam collapse. A simple parameter (relating the energy transmitted to a bubble from a ruptured neighbor and the energy needed to break a bubble) is used to describe the change in the probability for next bubble ruptures. If this parameter is close to zero, the rupture of a bubble has no influence in the rupture of the others but if its value is large enough the rupture of one bubble can produce an avalanche of ruptures which finally destroys all the bubble raft. Experimentally we change this parameter by changing the bulk viscosity.We also observed that depending on the bulk and surface properties of foam stabilizing agent, the size distribution of avalanches (number of bubbles ruptured during the avalanche) follows a power law as in Self Organized Criticality processes (The edge of chaos) we will discuss this observation.