The free (open) boundary condition (FBC) in viscoelastic flow simulations

Mitsoulis, E; Malamataris, NA

dc.contributor.author	Mitsoulis, E	en
dc.contributor.author	Malamataris, NA	en
dc.date.accessioned	2014-03-01T11:46:35Z
dc.date.available	2014-03-01T11:46:35Z
dc.date.issued	2011	en
dc.identifier.issn	19606206	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/37955
dc.subject	CEF model	en
dc.subject	Free (open) boundary condition	en
dc.subject	Newtonian fluid	en
dc.subject	Non-isothermal flows	en
dc.subject	Second-order fluid	en
dc.subject	Viscoelastic flows	en
dc.title	The free (open) boundary condition (FBC) in viscoelastic flow simulations	en
heal.type	other	en
heal.identifier.primary	10.1007/s12289-011-1071-6	en
heal.identifier.secondary	http://dx.doi.org/10.1007/s12289-011-1071-6	en
heal.publicationDate	2011	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. Meth. Fluids, 1992; 14:587-608) 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 explicit differential constitutive equations. As such we consider here the Criminale-Ericksen-Filbey (CEF) model, which also reduces to the Second-Order Fluid (SOF) for constant material parameters. The Finite Element Method (FEM) is used to provide numerical results in simple Poiseuille flow where analytical solutions exist for checking purposes. Then previous numerical results are checked against Newtonian highly non-isothermal flows in a 4:1 contraction. Finally, the FBC is used with the CEF fluid with data corresponding to a Boger fluid of constant material properties. Particular emphasis is based on a non-zero second normal-stress difference, which seems responsible for earlier loss of convergence. The results with the FBC are in excellent agreement with those obtained from long domains, due to the highly convective nature of viscoelastic flows, for which the FBC seems most appropriate. The FBC formulation for fixed-point (Picard-type) iterations is given in some detail, and the differences with the Newton-Raphson formulation are highlighted regarding some computational aspects. © 2011 Springer-Verlag France.	en
heal.journalName	International Journal of Material Forming	en
dc.identifier.doi	10.1007/s12289-011-1071-6	en
dc.identifier.spage	1	en
dc.identifier.epage	15	en