KURENAI : Kyoto University Research Information Repository

Substituting Eqs. (3) and (4) into Eq. (1), one gets the critical Weber number
to be
We c'= 817 .(5)
This value is much smaller than the one given by Eq. (2), however, it is
considered to be a more reliable criterion for large drops.
When a droplet is suddenly exposed into a gas stream, violent shatter-
ing of droplets becomes possible.. In this case, the critical Weber number is
about 10 to 12 for low viscous fluids _[13,18,20,21]. However, a significant
effect of the liquid viscosity has been observed. Thus Hinze [13] correlated
it in terms of the viscosity group (uf/pfDa) as
We c= 12
Later some
group as
1+
We c= 12 + 14
2
of
pfDo
0.36
In view of Eqs. s. (5) and (7), it may be concluded that the criterion given by
Eq. (7) is a good g general purpose correlation for droplet disintegrations in
gas stream.
2
of
p fDa
The third d mech mechanism is the disintegration of fluid particles by strong
turbulent motions ions c of a continuous phase [13,17]. This occurs mainly in bub-
bly flow or droplet roplet in liquid flow. For highly turbulent flow, the value of
the critical Weber number is given approximately [13,17] by
We 2 ti 2.5 .(8)
c= 1,2ti2.
has been
0.8
It is noted that hat th these critical Weber numbers are sensitive to flow conditions .
For example, in a p pulsating flow the value of We can be reduced by as much as
50% of the one e give given by Eq. (7).
proposed [12] using the same
dimensionless
Another import important but quite different type of generation of droplets is
associated with th ent entrainment of droplets at gas-liquid interfaces [1
,2,14]. In
158
(6)
(7)