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-   -   Uplus vs Yplus Non-Newtonian Fluids (http://www.cfd-online.com/Forums/fluent/109497-uplus-vs-yplus-non-newtonian-fluids.html)

C.C November 19, 2012 10:20

Uplus vs Yplus Non-Newtonian Fluids
 
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Hi all,

I want simulate a turbulent pipe flow of a non-Newtonian fluid... I'm looking for the representation of U+ as a function of y+, because I'm going change the log wall law taking into account a reference in the literature.
The non-newtonian behavior was translated by a power law (viscosity as a function of shear rate) that is available in Fluent for turbulent flow...
In the figure, the green line corresponds to the standard log-law considering the viscosity constant.
The U+ presents a strange behavior... Someone knows why I obtained this behavior, some references about the non-newtonian fluids and turbulence in CFD or how the non-newtonian behavior is implemented in the k-e turbulence model? Thank you

C.C November 19, 2012 13:09

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I've calculatd y+ with density and viscosity in each node, but I found a paper where the authors considered the mean wall viscosity instead of Newtonian viscosity. If I consider the mean wall viscosity the profiles seem be OK... what strategy is correct?

Someone knows if in the dimensionless distance (Attached Expression) http://www.cfd-online.com/Forums/dat...AAAElFTkSuQmCC http://www.cfd-online.com/Forums/dat...AAAElFTkSuQmCC the density and the viscosity when the fluid is non-newtonian is evaluated in each node or can be equal to mean wall viscosity?


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