O–W emulsions, regime TI ifZCis not much higher than that of water;
for a higher viscosity it tends to be regime TV, especially if the
resultingdis very small;
W–O emulsions: here,ZCis relatively large, and the regime will often
be TV. At small Re—as in a colloid mill—the regime is likely to be
LV.11.3.2 Laminar Flow
Two of the various types of laminar flow, and the effects such flows have on
drops, are depicted in Figure 11.7. It also gives the definitions of the velocity
gradient.
Simple shear flowcauses rotation, and also the liquid inside a drop
subjected to shear flow does rotate. The drop is also deformed, and the
relative deformation(i.e., the strain) is defined asD:ðLBÞ=ðLþBÞ; see
Figure 11.7a for definition ofLandB. For small Weber numbers, we simply
FIGURE11.7 Two types of laminar flow, and the effect on deformation and
breakup of drops at increasing velocity gradient (C). The flow is two-dimensional,
i.e., it does not vary in thez-direction. More precisely, the flow type in (b) is ‘‘plane
hyperbolic flow.’’