Deformation and break-up of a bubble in a diffusive turbulence

The deformation and the rupture of a bubble under the action of the turbulence of the liquid which surrounds it has been studied. In order to isolate the effects of turbulence from those of the mean velocity field, an original experimental device has been developed: an axisymmetric jet confined in a closed tube. At a certain distance from the jet, a turbulent vein where the energy of the mean movement is negligible and where the spatial integral scales are constant has been obtained. The turbulence is transported by itself through diffusion, its energy decreasing when moving away from the zone of production. The complete exploration of the velocity field by laser anemometry allowed to determine its properties (exponential decay, affinity of statistical moments) and to reveal original mechanisms of energy transfer between Reynolds tensions. The overall results prove that this experimental tool is suitable for studying the specific role of turbulence. Two-phase experiments, which consisted in filming the behavior of isolated bubbles in the turbulent field, have been conducted in microgravity conditions to eliminate the large slippage between the phases due to gravity. The turbulence intensity that is required to lead to bubble rupture was estimated; its value allows to conclude that, in the majority of the experiments conducted on the ground, the turbulence is not the preponderant phenomenon for the rupture. A study of the temporal evolution of the deformations of the interface was carried out from the processed images, giving information on the respective roles of turbulence and of the intrinsic dynamics of the bubble in the deformation and breakage processes