Annular extrudate swell of pseudoplastic and viscoplastic fluids

Mitsoulis, E

dc.contributor.author	Mitsoulis, E	en
dc.date.accessioned	2014-03-01T01:25:55Z
dc.date.available	2014-03-01T01:25:55Z
dc.date.issued	2007	en
dc.identifier.issn	0377-0257	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/17818
dc.subject	Annular flow	en
dc.subject	Blow molding	en
dc.subject	Exit correction	en
dc.subject	Extrudate swell	en
dc.subject	Herschel-Bulkley model	en
dc.subject	Power-law fluids	en
dc.subject	Pseudoplasticity	en
dc.subject	Viscoplasticity	en
dc.subject	Yield stress	en
dc.subject.classification	Mechanics	en
dc.subject.other	Blow molding	en
dc.subject.other	Computer simulation	en
dc.subject.other	Extrusion	en
dc.subject.other	Finite element method	en
dc.subject.other	Flow of fluids	en
dc.subject.other	Mathematical models	en
dc.subject.other	Viscoplasticity	en
dc.subject.other	Yield stress	en
dc.subject.other	Annular flow	en
dc.subject.other	Bingham number	en
dc.subject.other	Extrudate swell	en
dc.subject.other	Herschel-Bulkley model	en
dc.subject.other	Power-law index	en
dc.subject.other	Pseudoplasticity	en
dc.subject.other	Non Newtonian liquids	en
dc.subject.other	Blow molding	en
dc.subject.other	Computer simulation	en
dc.subject.other	Extrusion	en
dc.subject.other	Finite element method	en
dc.subject.other	Flow of fluids	en
dc.subject.other	Mathematical models	en
dc.subject.other	Non Newtonian liquids	en
dc.subject.other	Viscoplasticity	en
dc.subject.other	Yield stress	en
dc.title	Annular extrudate swell of pseudoplastic and viscoplastic fluids	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.jnnfm.2006.10.004	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.jnnfm.2006.10.004	en
heal.language	English	en
heal.publicationDate	2007	en
heal.abstract	Numerical simulations have been undertaken for the benchmark problem of annular extrudate swell present in pipe extrusion and parison formation in blow molding. The finite element method (FEM) is used to provide numerical results for different inner/outer diameter ratios kappa under steady-state conditions. The Herschel-Bulkley model of viscoplasticity is used with the Papanastasiou regularization, which reduces with appropriate parameter choices to the Bingham-Papanastasiou, power-law and Newtonian models. The present results provide the shape of the extrudate, and in particular the thickness and diameter swells, as a function of the dimensionless power-law index (in the case of pseudoplasticity) and the dimensionless yield stress (in the case of viscoplasticity). The pressures from the simulations have been used to compute the excess pressure losses in the system (exit correction). While shear-thinning leads to reduced swelling relative to the Newtonian values for all kappa-values, the opposite is true for shear-thickening fluids, which exhibit considerable swelling. Viscoplasticity leads to decreased extrudate swell as the dimensionless yield stress goes from zero (Newtonian behaviour) to an asymptotic value of fully plastic behaviour. The exit correction decreases to zero with a decrease in the power-law index to zero and an increase in the dimensionless yield stress to its asymptotic limit. However, the decrease is not monotonic: for power-law fluids it has maxima in the range of power-law indices between 0.8 and 0.6, while for viscoplastic fluids it has maxima around Bingham number values of 5. (c) 2006 Elsevier B.V. All rights reserved.	en
heal.publisher	ELSEVIER SCIENCE BV	en
heal.journalName	Journal of Non-Newtonian Fluid Mechanics	en
dc.identifier.doi	10.1016/j.jnnfm.2006.10.004	en
dc.identifier.isi	ISI:000244279100006	en
dc.identifier.volume	141	en
dc.identifier.issue	2-3	en
dc.identifier.spage	138	en
dc.identifier.epage	147	en