Effect of the contraction ratio upon viscoelastic fluid flow in three-dimensional square-square contractions

• Type: Article in International Scientific Journal
• Date: 2011

Authors

Sousa, PC (Author) FEUP; Coelho, PM (Author) FEUP; Oliveira, MSN (Author) Other; Alves, MA (Author) FEUP

Journal

Title: Chemical Engineering Science

Vol. 66 No. 11

Pages: 998-1009

ISSN: 0009-2509

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 18 Citations

ISI Web of Science

Scopus - 24 Citations

Scientific classification

FOS: Engineering and technology > Chemical engineering

Other information

Authenticus ID: P-002-TW2

DOI: 10.1016/j.ces.2010.12.011

Abstract (EN): In this work we investigate the laminar flow through square-square sudden contractions with various contraction ratios (CR=2.4, 4, 8 and 12), using a Newtonian fluid and a shear-thinning viscoelastic fluid. Visualizations of the flow patterns were carried out using streak line photography and detailed velocity field measurements were performed using particle image velocimetry. The experimental results are compared with numerical predictions obtained using a finite-volume method. For the Newtonian fluid, a corner vortex is found upstream of the contraction and increasing flow inertia leads to a reduction of the vortex size. Good agreement is observed between experiments and numerical simulations. For the shear-thinning fluid flow a corner vortex is also observed upstream of the contraction independently of the contraction ratio. Increasing the elasticity of the flow, while still maintaining low inertia flow conditions, leads to a strong increase of the vortex size, until an elastic instability sets in and the flow becomes time-dependent at De approximate to 200, 300, 70 and 450 for CR=2.4, 4, 8 and 12, respectively. At low contraction ratios, viscoelasticity brings out an anomalous divergent flow upstream of the contraction. For both fluids studied the flow presents a complex three-dimensional helical vortex structure which is well predicted by numerical simulations. However, for the viscoelastic fluid flow the maximum Deborah number achieved in the numerical simulations is about one order of magnitude lower than the critical Deborah number for the onset of the elastic instability found in the experiments.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 12