Entry flow of LDPE melts in a planar contraction

Mitsoulis, E; Schwetz, M; Munstedt, H

dc.contributor.author	Mitsoulis, E	en
dc.contributor.author	Schwetz, M	en
dc.contributor.author	Munstedt, H	en
dc.date.accessioned	2014-03-01T01:18:57Z
dc.date.available	2014-03-01T01:18:57Z
dc.date.issued	2003	en
dc.identifier.issn	0377-0257	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/15275
dc.subject	Extensional viscosity	en
dc.subject	Integral constitutive equations	en
dc.subject	Planar entry flow	en
dc.subject	Polymer melts	en
dc.subject	Viscoelasticity	en
dc.subject	Vortex growth	en
dc.subject.classification	Mechanics	en
dc.subject.other	Computer simulation	en
dc.subject.other	Laser Doppler velocimeters	en
dc.subject.other	Rheology	en
dc.subject.other	Shrinkage	en
dc.subject.other	Strain hardening	en
dc.subject.other	Vortex flow	en
dc.subject.other	Creeping entry flow	en
dc.subject.other	Low density polyethylenes	en
dc.subject.other	non-linear motion	en
dc.subject.other	polymer melt	en
dc.subject.other	rheology	en
dc.subject.other	shear flow	en
dc.subject.other	viscosity	en
dc.title	Entry flow of LDPE melts in a planar contraction	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/S0377-0257(03)00012-0	en
heal.identifier.secondary	http://dx.doi.org/10.1016/S0377-0257(03)00012-0	en
heal.language	English	en
heal.publicationDate	2003	en
heal.abstract	Experiments using laser-Doppler velocimetry (LDV) and numerical simulations have been undertaken for the creeping entry flow of two rheologically well-characterised low-density polyethylene (LDPE) melts in a 14:1 planar contraction. LDV measurements of the flow reveal a distinct behaviour between the two melts regarding vortex formation. The flow of the melts has been modelled using an integral constitutive equation of the K-BKZ type with a spectrum of relaxation times, modified to properly account for strain hardening in the planar extensional flow relevant for the geometry used. Numerical values for the constants appearing in the equation have been obtained from fitting dynamic data (G' and G") as well as data for the viscosities and normal stresses as measured in shear. Elongational data were derived from transient and steady uniaxial elongation experiments. The experiments show that for one LDPE melt the vortex keeps small with increasing flow rate, while for the other there is a vortex growth in the same range of flow rates. The numerical simulations also predict the same trend in agreement with the experiments. The differences in flow behaviour of the two branched melts are found to be attributed to big differences in the average relaxation times, giving rise to different De numbers or dimensionless stress ratios S-R, for the same range of flow rates. Equally important is the more pronounced extensional strain-hardening behaviour of the vortex-producing polymer, giving rise to high Trouton ratios T-R. (C) 2003 Elsevier Science 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/S0377-0257(03)00012-0	en
dc.identifier.isi	ISI:000181952200003	en
dc.identifier.volume	111	en
dc.identifier.issue	1	en
dc.identifier.spage	41	en
dc.identifier.epage	61	en