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Title: Fracture of the free surface of a complex fluid undergoing shear banding
Author: Skorski, Stanislav
ISNI:       0000 0004 2746 0330
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2012
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Meniscus distortion and fracture during shear occurs frequently in non-Newtonian fluids. Similar instabilities at the free surface of fluids undergoing shear banding have been reported; in some cases the sample was expelled from the cell. In this thesis, the distortion of the free surface of such a shear banding fluid is calculated by balancing the surface tension against the second normal stresses induced in the two shear bands, and simultaneously requiring a continuous and smooth meniscus. It is shown that solutions of worm-like micelles typically retain meniscus integrity when shear banding, but in some cases can lose integrity for a range of average applied shear rates over which one expects shear banding. This meniscus fracture would lead to ejection of the sample as the shear rate is increased within the shear banding range. It is shown further that solutions of entangled polymer are expected to display a propensity for fracture because of their much larger second normal stresses. These calculations are consistent with available data in the literature. Also considered is the meniscus distortion of a three-band configuration, as has been observed in some worm-like micellar solutions in a cone and plate geometry.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available