String breakup

FIGURE ISM Breakup cC a Qrlindiical p[Pg.802]

A long, stationary droplet or "thread" of one fluid in another can break up into a string of smaller droplets, and this breakup mechanism has been further treated for slowly moving bubbles by Flumerfelt and co-workers (69,70). In tubes, thread breakup produces bubbles whose lengths are on the order of four times the diameter of the unbroken thread. The incorporation of this mechanism into a constricted tube model for dispersion flow in porous media is described in the chapter by Prieditis and Flumerfelt. 

Y arin et al. [29, 111] gave a theory of the capillary breakup of thin jets of dilute polymer solutions and formation of the bead-OTi-the-string structure (some additional later results can be foimd in [90]). The basic quasi-one-dimensional equations of capillary jets (1.49) and (1.50) are supplemented with an appropriate viscoelastic model for the longitudinal stress. Yarin et al. [29, 111] used the Hinch rheological constitutive model, which yields the following expression... 

Upon cessation of flow, well-known interfacial tension driven flow instabilities set in and cause catastrophic breakup of the strings into droplets. 

Fig. 3.73 Dislocation substructure in -doped sapphire deformed 2.5 % on basal plane at 1520 °C. Strings of loops resulting from breakup of dipoles by self-climb are apparent. Basal foil [38]. With kind permission of John Wiley and Sons...

Migler K B (2001) String formation in sheared polymer blends coalescence, breakup, and finite size effects, Phys Rev Lett 86 1023-1026. 

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