The effect of the expansion ratio on a turbulent non-Newtonian recirculating flow |
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Authors: | A S Pereira F T Pinho |
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Institution: | Departamento de Engenharia Química Instituto Superior de Engenharia do Porto Rua de S?o Tomé 4200 Porto, Portugal, PT Centro de Estudos de Fenómenos de Transporte, DEMEGI, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200–465 Porto, Portugal e-mail: fpinho@fe.up.pt, PT
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Abstract: | Measurements of the mean and turbulent flow characteristics of shear-thinning moderately elastic 0.1% and 0.2% xanthan gum
aqueous solutions were carried out in a sudden expansion having a diameter ratio of 2. The inlet flow was turbulent and fully
developed, and the results were compared with data for water in the same geometry and with previous published Newtonian and
non-Newtonian data in a smaller expansion of diameter ratio equal to 1.538. An increase in expansion ratio led to an increase
in the recirculation length and in the axial normal Reynolds stress at identical normalised locations, but the difference
between Newtonian and non-Newtonian characteristics was less intense than in the smaller expansion. An extensive comparison
of mean and turbulent flow characteristics was carried out in order to understand the variation of flow features.
Received: 31 July 2000 / Accepted: 27 August 2001 |
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