Drop elongation

Figure 1.13. Mechanism of rupturing. Under shear, drops elongate into long cylinders (a) that undergo a Rayleigh instability leading to identical aligned droplets (b). (Adapted from [149].)...

This method is particularly useful for the measurement of very low interfacial tensions (<10 mN m ) that are particularly important in applications such as spontaneous emulsification and the formation of microemulsions. Such low interfacial tensions may also be achieved with emulsions, particularly when mixed surfactant films are used. In this case, a drop of the less-dense liquid A is suspended in a tube containing the second liquid, B. On rotating the whole mass (see Figure 5.4) the drop of the liquid moves to the centre and, with an increasing speed of revolution, the drop elongates as the centrifugal force opposes the interfacial tension force that tends to maintain the spherical shape, which is that having a minimum surface area. 

Rheometer Experimental and theoretical study of drop elongation in a steady-state flow, at constant shear stresses. Lyngaae-Jprgensen et al., 1991, 1993. 

Well, yes, Meitner said, that is what I mean. She had meant to draw what Frisch had drawn, a liquid drop elongated like a dumbbell, but had drawn it end-on, indicating with a smaller dashed circle inside a larger solid circle the dumbbell s waist. 

When drop elongation exceeds a certain value, the drop breaks up into smaller drops a is related to the capillary number n,... 

It is believed that the first normal force difference plays a key role in the drop elongation along the vorticity axis. Hobbie and Migler [6] showed that contraction in flow direction begins when normal and shear stresses are of similar magnitude. Based on this observation, here we give an estimate of the lower limit of drop size above which the drop will break up in flow direction. 

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