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Short wave instability of co-extruded elastic liquids with matched viscosities.

Wilson, HJ; Rallison, JM; (1997) Short wave instability of co-extruded elastic liquids with matched viscosities. Journal of Non-Newtonian Fluid Mechanics , 72 (2-3) 237 - 251. 10.1016/S0377-0257(97)00025-6. Green open access

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Abstract

The stability of channel flow of coextruded elastic liquids having matched viscosities but a jump in elastic properties is studied. Inertia and surface tension are neglected. A short wave disturbance is found, confined near the interface, whose growth rate is independent of wavelength. For dilute Oldroyd-B fluids this disturbance is unstable for any non-zero jump in normal stresses, and has a maximum growth rate for intermediate levels of elasticity in the two fluids. When one or other fluid is highly elastic the growth rate falls. In the concentrated limit (a UCM fluid), the disturbance is unstable only for a finite range of normal stress jumps, and is restabilized if one fluid is much more elastic than the other. Because the short wave disturbance is localised, the results apply for any steadily sheared interface across which the normal stress jumps. The results are confirmed for moderate parameter values by means of a full numerical solution for a three-layer planar flow.

Type: Article
Title: Short wave instability of co-extruded elastic liquids with matched viscosities.
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/S0377-0257(97)00025-6
Publisher version: http://dx.doi.org/10.1016/S0377-0257(97)00025-6
Language: English
Additional information: This is the author’s version of a work that was accepted for publication in Journal of Non-Newtonian Fluid Mechanics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Non-Newtonian Fluid Mechanics, [VOL 72, ISSUE2-3, (1997)] DOI: 10.1016/S0377-0257(97)00025-6
Keywords: Co-extrusion, Core-annular flow, Short wave, Instability, Oldroyd-B, UCM, Normal stresses
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Mathematics
URI: https://discovery.ucl.ac.uk/id/eprint/113349
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