Review of experimental study on drop breakup time and breakup
rate
In this study, we mainly focus on the breakup time and breakup rate
generated upon drop breakup. Corresponding researches in the literature
were reviewed in this section.
The drop breakup time is an important parameter to understand the
mechanism of drop breakup. At present, the parameter was obtained mainly
by single drop experiments. Heskech et al.42 measured
a limited number of drop breakup events and obtained the breakup time of
silicone oil in a horizontal pipeline. The results showed that the
breakup time was 19-59 ms for the mother drop with size 3.40-4.55 mm.
Eastwood et al.16 found that the elongated drop can
break up owing to capillary effects. Meanwhile, they pointed out that
the viscosity of the dispersed phase is an important parameter affecting
the breakup time. Andersson and Andersson43 carried
out single drop breakup experiments in turbulent flows. They compared
the breakup time of drops with the turbulent time scales and pointed out
that only large turbulent eddies are effective in drop
breakup43. Maaß and Kraume30investigated the drop breakup time in a rectangular channel where a
single blade was fixed internally. Their statistical criterion of
breakup time is the duration of the whole process from the drop entering
the flow field to the final breakup. It should be noted that this time
often includes circulation time, where the drop may remain subspherical.
On the premise above, they found that the breakup time is not a const
but approximately obey a β -distribution for the drop of a certain
size. Furthermore, they discussed the breakup time based on the peak
values of the β -distribution. Experimental data showed that the
breakup time monotonically increases with increasing of the drop
diameter and decreases with increasing of the energy dissipation rate.
Solsvik and Jakobsen34 measured the breakup time by
single drop breakup experiments in a stirred tank. They scaled the
breakup time as the duration taken from the initial deformation of a
spherical mother drop to the terminus where the fragments were totally
generated. They further defined the breakup process as the breakup
cascade37. According to their study, the breakup time
holds a significant dependence on the drop diameter and increases
monotonously with the increase of drop size. Ashar et
al.36 measured the time for droplet deformation in a
rotor-stator mixer. They found out that the breakup time is positively
scaled with the weber number. Meanwhile, they point out that turbulent
eddies with the size close to the target drop control the breakup
process.
Despite researchers provided important experimental data of drop breakup
time through single drop experiments, the quantitative laws of how
physical properties and operating parameters influence the breakup time
are still limited. Moreover, the sufficiently predictable model for drop
breakup time is also in lack.
Recently, experiments have been carried out by Li’s group to measure the
breakup rate directly in a pulsed disc and doughnut
column38–40,44 and in a
pump-mixer41,45. In the above study, the multiple
breakup process is treated mathematically as a sequence of the binary
breakup. In this study, experimental data of the breakup rate are also
provided. Moreover, we make a systematic analysis of the process of
multiple breakage and probe into the influence rules of different
factors on multiple breakup.