Learning Forum

[Isao.Tsujimura]

I am using FLUENT to perform flow analysis, but I would like to know about the viscosity equation. When fitting the viscosity equation using POLYDATA with viscosity measurements obtained by changing the extrusion temperature of a polymer, I selected the Arrhenius temperature-dependent equation for temperature dependence, and the CROSS model for the viscosity equation. I performed a flow analysis, but the inlet pressure became abnormally high, and I think the viscosity equation is suspicious. The viscosity equation and temperature-dependent equation in the FLUENT user guide do not match those of POLYDATA. In particular, the power law exponent n is a single parameter in the POLYDATA CROSS model, which is (1-n), but in the FLUENT CROSS model, the power of the multiplication of shear rate and λ is 1-n, which is different. Please tell me which viscosity equation is used for calculations in actual flow analysis.

[Rob]

Fluent will use the Fluent model, and Poly data (Polyflow) will use it's own documented equivalent. 

[Isao.Tsujimura]

Thank you for your reply.

Please clearly state the formulation of Fluent and POLYDATA's CROSS model and Arrhenius model. Also, please tell me the units of the parameters to be entered into each model.

I use POLYDATA to fit the viscosity equation. If I want to use the parameters obtained from the CROSS model and Arrhenius model fitted with POLYDATA in the CROSS model and Arrhenius model of FLUENT, how should I change each parameter to get correct calculations?

[Rob]

Please refer to the documentation.