Formation of viscoplastic drops by capillary breakup

The process of growth and detachment of drops from a capillary nozzle is studied experimentally by high-speed imaging. Newtonian drops are compared to shear-thinning and viscoplastic drops. Both Newtonian and shear-thinning fluid drops grow on the end of the capillary until a maximum supportable ten...

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Bibliographic Details
Published in:Physics of fluids (1994) 2010-03, Vol.22 (3), p.033101-033101-11
Main Authors: German, G., Bertola, V.
Format: Article
Language:English
Subjects:
Drops and bubbles
Exact sciences and technology
Fluid dynamics
Fundamental areas of phenomenology (including applications)
Hydrodynamic stability
Non-newtonian fluid flows
Nonhomogeneous flows
Physics
Surface-tension-driven instability
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Summary:The process of growth and detachment of drops from a capillary nozzle is studied experimentally by high-speed imaging. Newtonian drops are compared to shear-thinning and viscoplastic drops. Both Newtonian and shear-thinning fluid drops grow on the end of the capillary until a maximum supportable tensile stress is reached in the drop neck, after which they become unstable and detach. The critical stress is not influenced by variations in viscosity or in the degree of shear thinning. Viscoplastic fluids show a different behavior: at low values of the yield stress, the critical stability behavior is similar to that of Newtonian and shear-thinning drops. Above a threshold value, characterized in terms of the drop size, surface tension and tensile yield-stress magnitude, yield-stress forces are larger than surface forces, and the maximum tensile stress achievable in the drop neck at the point of critical stability is governed by the von Mises criterion.
ISSN:1070-6631
1089-7666
DOI:10.1063/1.3339783