Civil and Environmental Engineering Publications
A numerical study of dean instability in non-Newtonian fluids
Document Type
Article
Publication Date
2006
Journal
JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
Volume
128
Issue
1
First Page
34
URL with Digital Object Identifier
https://doi.org/10.1115/1.2136926
Last Page
41
Abstract
We present a numerical study of Dean instability for non-Newtonian fluids in a laminar 180 deg curved-channel flow of rectangular cross section. A methodology based on the Papanastasiou model (Papanastasiou, T C., 1987, J. Rheol., 31(5), pp. 385-404) was developed to take into account the Bingham-type theological behavior. After validation of the numerical methodology, simulations were carried out (using FLUENT CFD code) for Newtonian and non-Newtonian fluids in curved channels of square or rectangular cross section and for a large aspect and curvature ratios. A criterion based on the axial velocity gradient was defined to detect the instability threshold. This criterion was used to optimize the grid geometry. The effects of curvature and aspect ratio on the Dean instability arc, studied for all fluids, Newtonian and non-Newtonian. In particular, we show that the critical value of the Dean number decreases with increasing curvature ratio. The variation of the critical Dean number with aspect ratio is less regular The results art compared to those for Newtonian fluids to emphasize the effect of the power-law index and the Bingham number The onset of Dean instability is delayed with increasing power-law index. The same delay is observed in Bingham fluids when the Bingham number is increased.