KURENAI : Kyoto University Research Information Repository

• Equation
£ ^ D
Substituting Eqs. (48) and (49) into Eq. (47), one obtains
where
and
terms
Then
* *3/4
vi v
g
*
Vi vi
Vg
The
vg
of
Eq.
°°gl( agop
gas
void
jg
a (50)
velocity
N1/4
u9 D*-1/4
pf
6gop
Pg)1/4
fraction
can
Pg 1/4
vg is
a in
1/2
related' to
the liquid
be rewritten as
the
pool
superficial gas
v.j93/4a-3/4N1g4D (Pg\l/2(54)
1f
as
(49)
(50)
(51)
(52)
velocity jg in
(54) is derived from the consideration of the momentum exchange
mechanism at the interface. However, there are some experimental data for vi,
which support the dependence of vi on jg and D as given by Eq. (54).
Akselrod et al. [62] and Cheng et al. [28] measured indirectly
(calculated from the maximum height of a droplet) the droplet initial velocity
in an air-water system at the atmospheric pressure. In their experiment, the
269
(53)