  Breaking waves generate a distribution of bubble sizes that evolves over
time. Knowledge of how this distribution evolves is of practical importance for
maritime and climate studies. The analytical framework developed in Part 1
examined how this evolution is governed by the bubble-mass flux from large to
small bubble sizes, which depends on the rate of break-up events and the
distribution of child bubble sizes. These statistics are measured in Part 2 as
ensemble-averaged functions of time by simulating ensembles of breaking waves,
and identifying and tracking individual bubbles and their break-up events. The
break-up dynamics are seen to be statistically unsteady, and two intervals with
distinct characteristics were identified. In the first interval, the
dissipation rate and bubble-mass flux are quasi-steady, and the theoretical
analysis of Part 1 is supported by all observed statistics, including the
expected -10/3 power-law exponent for the super-Hinze-scale size distribution.
Strong locality is observed in the corresponding bubble-mass flux, supporting
the presence of a super-Hinze-scale break-up cascade. In the second interval,
the dissipation rate decays, and the bubble-mass flux increases as small- and
intermediate-sized bubbles become more populous. This flux remains strongly
local with cascade-like behaviour, but the dominant power-law exponent for the
size distribution increases to -8/3 as small bubbles are also depleted more
quickly. This suggests the emergence of different physical mechanisms during
different phases of the breaking-wave evolution, although size-local break-up
remains a dominant theme. Parts 1 and 2 present an analytical toolkit for
population balance analysis in two-phase flows.
