Learning Forum

[Francesc Riera]

Hi, I'm trying to simulate the shear thickening behaviour of some non-newtonian fluids and I'm a bit lost about how could I make it. I'm trying with ansys CFX using immersed solid to replicate a granular solution with this behaviour but I still can't get anything similar. I don't know if I should try with fluent insted. If someone know anything about how to simulate shear thickening fluids it would be a grat help. Thanks.

[Rob]

It's a fluid property, and I'm not sure why you're trying the immersed solids for a granular mixture. I don't use CFX but think that's intended for "big" bits of geometry. 

In Fluent (and CFX) you can alter the material viscosity using a few pre-set options or add user functions to add your own model. 

[Francesc Riera]

Thanks Rob!

This means that if I change the viscosity properties of a fluid to a "non-newtonian-power-law" and then set the appropriate consistency index (k) and a power law index (n) greater than 1, the fluid that I'm trying to simulate will it behave like a shear thickening fluid? Would this be enough or do I need to change something in "models"? Or do you recommend I add my own model?

[Rob]

Pretty much. Non-Newtonian fluids tend to fit some models better than others, so some are good with the Power Law, others need Carreau etc. I can't comment whether Power Law is "best", but do suggest plotting the curves to confirm (experimental data v model). Not sure about what else needs to be adjusted in CFX (I haven't used it in years and wasn't overly proficient when I did); in Fluent you need to turn off turbulence or mess with a command line option.