Detection of the onset of Dean instability and effects of the rheological behavior in non-Newotonian fluids

Start The onset of Dean instability in laminar secondary flow in 180° curved rectangular cross section channel was studied experimentally and numerically in Newtonian and non-Newtonian fluids. The development of the instability was observed; we showed that the Dean vortices develop first in the near...

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Bibliographic Details
Published in:Journal of physics. Conference series 2008-11, Vol.137 (1), p.012023
Main Authors: Fellouah, H, Castelain, C, Moctar, A Ould El, Peerhossaini, H
Format: Article
Language:English
Subjects:
Concave walls
Criteria
Cross-sections
Flow stability
Fluid flow
Laminar flow
Newtonian fluids
Non Newtonian fluids
Physics
Pseudoplasticity
Rheological properties
Secondary flow
Shear rate
Viscosity
Visualization
Vortices
Citations: Items that this one cites
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Summary:Start The onset of Dean instability in laminar secondary flow in 180° curved rectangular cross section channel was studied experimentally and numerically in Newtonian and non-Newtonian fluids. The development of the instability was observed; we showed that the Dean vortices develop first in the near wall zone on the concave wall, where the viscosity is weak and the shear rate is high, and than they penetrate the cross-section center characterized by a high viscosity for the pseudoplastic fluids and a solid (unsheared) zone for the yield fluids. Based on the complete formation of the Dean vortices, the critical value of the Dean number decreases with the increase of the power law index and with the decrease of the Bingham number. Contrarily to what is reported in the literature where the instability threshold was usually obtained visually, in this study a new criterion based on the radial gradient of the axial velocity to detect the instability threshold was defined. Comparison was made between numerical and experimental results concerning the instability threshold, obtained with the new criterion. Also, a comparison between the instability threshold using this new criterion and using the visualization technique is presented. We show that the value of the Dean number using the new criterion is comparable for the two studies, numerical and experimental. These values are weaker than those obtained with the visualization technique for the same conditions.your abstract here...
ISSN:1742-6596
1742-6588
1742-6596
DOI:10.1088/1742-6596/137/1/012023