The free (open) boundary condition with integral constitutive equations

Mitsoulis, E; Malamataris, NA

dc.contributor.author	Mitsoulis, E	en
dc.contributor.author	Malamataris, NA	en
dc.date.accessioned	2014-03-01T02:14:49Z
dc.date.available	2014-03-01T02:14:49Z
dc.date.issued	2012	en
dc.identifier.issn	03770257	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/30128
dc.subject	Free (open) boundary condition	en
dc.subject	Integral Maxwell fluid	en
dc.subject	K-BKZ model	en
dc.subject	Newtonian fluid	en
dc.subject	Non-isothermal flows	en
dc.subject	Viscoelastic flows	en
dc.subject.other	Finite element method FEM	en
dc.subject.other	Material parameter	en
dc.subject.other	Maxwell fluid	en
dc.subject.other	Newtonian fluids	en
dc.subject.other	Nonisothermal flows	en
dc.subject.other	Numerical results	en
dc.subject.other	Outflow condition	en
dc.subject.other	Planar flow	en
dc.subject.other	Poiseuille flow	en
dc.subject.other	Single relaxation time	en
dc.subject.other	Test case	en
dc.subject.other	UCM model	en
dc.subject.other	Upper-convected maxwell fluids	en
dc.subject.other	Visco-elastic fluid	en
dc.subject.other	Viscoelastic flows	en
dc.subject.other	Boundary conditions	en
dc.subject.other	Constitutive equations	en
dc.subject.other	Finite element method	en
dc.subject.other	Maxwell equations	en
dc.subject.other	Polymer melts	en
dc.subject.other	Viscoelasticity	en
dc.subject.other	Integral equations	en
dc.title	The free (open) boundary condition with integral constitutive equations	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.jnnfm.2012.04.009	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.jnnfm.2012.04.009	en
heal.publicationDate	2012	en
heal.abstract	The free (or open) boundary condition (FBC, OBC) was proposed by Papanastasiou et al. (A new outflow boundary condition, Int. J. Numer. Methods Fluids 14 (1992) 587-608) to handle truncated domains with synthetic boundaries where the outflow conditions are unknown. In the present work, implementation of the FBC has been extended to viscoelastic fluids governed by integral constitutive equations. As such we consider here the K-BKZ/PSM model, which also reduces to the upper-convected Maxwell fluid (UCM) for a single relaxation time and an appropriate choice of material parameters. The Finite Element Method (FEM) is used to provide numerical results in simple test cases, such as planar flow at an angle and Poiseuille flow in a tube where analytical solutions exist for checking purposes. Then previous numerical results obtained with the differential UCM model are checked in highly viscoelastic flows in a 4:1 contraction. Finally, the FBC is used with the K-BKZ/PSM model with data corresponding to a benchmark polymer melt (the IUPAC-LDPE melt). Particular emphasis is based on a non-zero second normal-stress difference, which has been reported in the literature to cause problems and seems responsible for earlier loss of convergence. The results with the FBC in short domains are in excellent agreement with those obtained from long domains used until now to accommodate the highly convective nature of the stresses in viscoelastic flows, for which the FBC seems most appropriate. © 2012 Elsevier B.V.	en
heal.journalName	Journal of Non-Newtonian Fluid Mechanics	en
dc.identifier.doi	10.1016/j.jnnfm.2012.04.009	en
dc.identifier.volume	177-178	en
dc.identifier.spage	97	en
dc.identifier.epage	108	en