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Author(s): M. A. Alves
F. T. Pinho
P. J. Oliveira
Title: Visualizations of viscoelastic flow in a 4:1 square/square contraction
Issue Date: 2004
Abstract: Visualizations of the three-dimensional flow in a 4:1 square-square sudden contraction were carried out for aNewtonian and two viscoelastic fluids under conditions of negligible inertia. In the case of the Newtonian fluid theinfluence of inertia was also studied, and for Reynolds numbers above 0.1 a significant decrease of the recirculationwas observed. In the case of viscoelastic fluids increasing the flowrate lead to different flow patterns depending onthe Deborah number and the type of viscoelastic fluid: whereas for the Boger fluid a complex flow pattern wasobserved, with a decrease on the vortex size up to Deborah numbers of 0.2, followed by a moderate increase up toDeborah values of 0.8, for the shear-thinning viscoelastic fluid there was a dramatic increase on the size of thevortex. With both viscoelastic fluids an elastic instability lead to the onset of a periodic flow at high flowrates(under conditions of negligible inertia). For the shear-thinning viscoelastic fluid the periodic flow was characterizedby a constant Strouhal number of 0.5. In the steady flow regime the vortices are not closed: fluid particles enter themiddle-plane vortex, rotate towards its eye, drift to the diagonal-plane vortex, then rotate to its periphery and exit tothe downstream duct, a dynamic process that is opposite to that observed and predicted numerically for Newtonianfluids.
Subject: Ciências da engenharia e tecnologias
Engineering and technology
Scientific areas: Ciências da engenharia e tecnologias
Engineering and technology
Source: 12th International Symposium on Applications of Laser Techniques to Fluid Mechanics
Document Type: Artigo em Livro de Atas de Conferência Internacional
Rights: restrictedAccess
Appears in Collections:FEUP - Artigo em Livro de Atas de Conferência Internacional

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