Experiments with nano-scaled helium bubbles in water subjected to standing acoustic fields

Understanding the stability of gas filled bubbles dispersed in water, and the features that due to their presence must been taken into account in multiphase flow research, is amongst the most recent and relevant issue in a number of technological, physical and biological fields. Cavitation experiments were designed and conducted using one high-Q acoustic resonator that is able to oscillate at very well controlled conditions, allowing for the characterization of the effect that helium nanobubbles dispersed in water have on the cavitation activity. An increase in the inertial cavitation activity that correlates directly to the presence of the nanobubbles at the antinode was found. The results seem to indicate that the nanobubbles grow under tension to collapse under the compression phase. By other side, they behave as rigid entities under the influence of standing acoustic fields, moving away from the antinode region.