8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P9.24Tue 611:23-14:00Bubbles dynamics in complex fluidsFlorence Haudin, 1 Christophe Raufaste, 1 and Xavier Noblin 11 LPMC, UMR 6622, CNRS-UNSA, Parc Valrose, 06108, Nice, FranceFrom the gas ex-solution of a freshly open Champagne bottle to the damaging consequences ofcavitation, numerous studies have already been dedicated to the formation of bubbles generatedby a pressure decrease in simple liquids. It is now well established that such phenomenon hasmajor implications in more complex environments, for instance in plant biophysics (cavitation inconfined structures of trees) or geophysical processes (magma decompression). We will present anexperimental study of bubbles formation and organization inside a viscoelastic material throughpressure decrease. A 2D geometry setup (Hele-Shaw cell) is chosen for simplicity: a gel is preparedand sandwiched between two glass plates. After the gelification process, a vacuum pumpis connected to the cell to decrease the pressure inside the complex fluid. The pressure is continuouslyrecorded and evolution of the dynamics is followed by a digital camera. As pressuredecreases, the gas initially dissolved in the hydrogel induces bubbles formation. Different stepsof the process are observed and analyzed: bubbles nucleation, growth, interactions and formationof domains. Viscoelastic properties of the material are tuned by adapting the gelling agent concentration.For low concentrations, bubbles tend to be circular as in a liquid whereas for largerconcentrations, anisotropic cavities and crack-like shapes are forming as in a solid. The interactionsbetween bubbles and the patterns formed can also be very different, depending on the fluidrheology.24