ICA 2010 paper

Multibubble effects on cavitation inception are studied in detail to show that bubble-bubble interaction can change the inception process of cavitation in a variety of ways. In an effort to develop a high-power pulsed neutron source which uses a giant proton accelerator and liquid mercury, we have attempted to use microbubbles to reduce cavitation damage of the mercury vessels caused by proton-induced intense pressure waves. From an off-line experiment, we found that cavitation of liquid mercury is suppressed by injecting a sufficient amount of gas microbubbles into mercury. This observation was the starting point of our multibubble study on cavitation inception. Using a simple multibubble model in which Rayleigh−Plesset type equations are coupled through the bubble-emitted pressure waves, we first showed that microbubbles can in certain cases suppress explosive growth of cavitation bubbles under negative pressure, implying a significant effect of injected microbubbles on cavitation inception. We then performed a more detailed numerical study on cavitation in multibubble cases and found that several different patterns of bubble dynamics, such as competitive growth and interrupted expansion, are possible in the early stage of cavitation. From this detailed study we also found that the instantaneous unstable equilibrium radii of growing bubbles play an essential role in these processes. These findings unveil the complex nature of interacting bubbles under negative pressure.