I am trying to model the viscosity of polymer using Carreau model. However, the options of Carreau model is not available for turbulent flow. So I am trying to write UDF in order to model the viscosity of polymer using Carreau model in turbulent flow. Anyone can help?
You can use DEFINE_TURBULENT_VISCOSITY macro and after writing the UDF, you may hook it in define/model/viscous panel.
The reason why the Carreau model is not offered for turbulent flow may be that non-Newtonian behaviour, especially when it is anisotropic and molecules are oriented along shear surfaces - as common in polymers, makes most of the assumptions underlying the classical RANS models invalid. So you will have to ask the question if your turbulent modelling is a good representation of the turbulent behaviour of the flow. Polymers have been shown to have a curious effect on turbulence (2D turbulence).
So while you might get away with a simple non-Newtonian viscosity model for polymers (like Carreau), I'd be very sceptical of its validity for turbulent flow.
Shell did a lot of research in that area, and there is FENE-P, which was extended to turbulence (k-epsilon):
http://www.sciencedirect.com/science/article/pii/S0377025711000784
Ali: Won't DEFINE_TURBULENT_VISCOSITY replace the turbulent model? If yes, that may be an interesting approach to combine turbulent viscosity and a non-Newtonian contribution.
To be honest, DEFINE_TURBULENT_VISCOSITY macro replaces the new definition of viscosity in turbulent model. If you would like use the default one and add some extra expression, you can do it by this macro, too. You can combine the default turbulent viscosity and others.
- Badges
- Science topic