  The inception of cavitation in multibubble cases is studied numerically and
theoretically to show that it is different from that in single-bubble cases in
several aspects. Using a multibubble model based on the Rayleigh-Plesset
equation with an acoustic interaction term, we confirmed that the recently
reported suppression of cavitation inception due to the interaction of
non-identical bubbles can take place not only in liquid mercury but also in
water, and we found that a relatively large bubble can significantly decrease
the cavitation threshold pressure of a nearby small bubble. By examining in
detail the transition region where the dynamics of the suppressed bubble
changes drastically as the inter-bubble distance changes, we determined that
the explosive expansion of a bubble under negative pressure can be interrupted
and turn into collapse even though the far-field liquid pressure well exceeds
the bubble's threshold pressure. Numerical results suggest that the
interruption of expansion occurs when the bubble radius is exceeded by the
instantaneous unstable equilibrium radius of the bubble determined using the
total pressure acting on the bubble. When we extended the discussion to systems
of larger numbers of bubbles, we found that a larger number of bubbles have a
stronger suppression effect. The present findings would be useful in
understanding the complex behavior of cavitation bubbles in practical
applications where in general many cavitation nuclei exist and may interact
with each other.
