Biomedical Engineering Reference
In-Depth Information
FIGURE 3.26
Concentration of species X within a water droplet carried by oil for s ¼
10
3
N/m at t
10
3
,
3.65
¼
0, 2
10
3
,6
10
3
,8
10
3
and 10
10
3
s.
4
where
T
T
o
T
o
T
¼
(3.59d)
10
3
N
s
o
¼
3
:
65
=
m
(3.59e)
10
2
m
o
¼
2
:
38
Pa
:
S
(3.59f)
10
4
S (3.59g)
The variations of these properties as temperature changes are plotted in
Fig. 3.29
. Of particular interest
is the variation of surface tension. This spatial variation of surface tension induced by the temperature
field generates an additional Marangoni force (second term in Eqn
3.36a
, i.e.,
m
þ
o
¼
9
:
00
Pa
:
ð N
VsÞ NdðfÞ
) that
drives flows. The net effect of the Marangoni force, in this context, is to drive the microdroplets
dynamically toward the region of higher temperature. This temperature-induced phenomenon is called
thermocapillary effect.
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