A comprehensive experimental investigation of tubular entry flow of viscoelastic fluids: Part III. Unstable flow

Authors

  • P. J. Cable,

    1. Department of Chemical Engineering, Monash University, Clayton, Victoria, Australia
    Current affiliation:
    1. ICI Limited, Ascot Vale, Victoria, Australia
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  • D. V. Boger

    Corresponding author
    1. Department of Chemical Engineering, University of Delaware, Newark, Delaware 19711
    • Monash University, Clayton, Victoria, Australia
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Abstract

For every viscoelastic fluid studied in the contraction geometry, it was found that increasing the flow rate beyond a certain limit resulted in disturbance to the stable entry flow patterns described in Parts I and II. An examination of the development of the entry flow disturbances was carried out using still and cine photography. Still photographs are presented to illustrate the characteristics of the unstable flow patterns. The time varying nature of the flow has been recorded on a cine film Flow Patterns in Abrupt Entry Flow of Viscoelastic Fluids which is available for loan. Critical condition criteria for the onset of the periodic flow disturbances were obtained in terms of the fundamental fluid properties and are presented and compared with other suggested criteria for the onset of unstable entry flow of viscoelastic fluids.

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