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Non-Newtonian models in COMSOL
Posted Jan 3, 2015, 10:48 p.m. EST Fluid & Heat, Computational Fluid Dynamics (CFD), Materials, Parameters, Variables, & Functions Version 5.0, Version 5.2 2 Replies
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HI,
I am re-posting this as I didn't receive a lot of attention last time. I have only seen Carreau and PowerLaw models for non-Newtonian flows in COMSOL. However, I want to implement a different constitutive relation of my own that involves some constants and has it's own unique functional form in the CFD module for non-Newtonian flow! The independent variable is still shear rate (gamma dot) but it is a different function than Carreau.
Does anyone how to define this function and then how to call it for calculation of the viscosity for a non-Newtonian flow simulation?
I am re-posting this as I didn't receive a lot of attention last time. I have only seen Carreau and PowerLaw models for non-Newtonian flows in COMSOL. However, I want to implement a different constitutive relation of my own that involves some constants and has it's own unique functional form in the CFD module for non-Newtonian flow! The independent variable is still shear rate (gamma dot) but it is a different function than Carreau.
Does anyone how to define this function and then how to call it for calculation of the viscosity for a non-Newtonian flow simulation?
2 Replies Last Post Jan 7, 2015, 7:10 p.m. EST
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Posted:
10 years ago
Hi,
i defined my own analytic function in the "Materials" sub-categories. My function (its the Cross-Wlf-model) depends on the shearrate and temperature.
You can use the automatic calculated shearrate as the function argument.
In my case its called "tpf.sr". Tpf for the two-phase-flow and sr for shearrate. You have to look how your shearrate variable is named.
Greets
Ingo
i defined my own analytic function in the "Materials" sub-categories. My function (its the Cross-Wlf-model) depends on the shearrate and temperature.
You can use the automatic calculated shearrate as the function argument.
In my case its called "tpf.sr". Tpf for the two-phase-flow and sr for shearrate. You have to look how your shearrate variable is named.
Greets
Ingo
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Posted:
10 years ago
Hello Ingo,
Thanks a lot for the advice. Turns out I have to use spf.sr for my definition. That brings the question, however, weather the single phase flow is a good assumption?
I get the the error: "Failed to find a solution for the initial parameter.
Maximum number of Newton iterations reached.
Returned solution is not converged."
I changed the settings in the solver but no luck. Maybe a two phase flow non-linear stationary solver is better choice? Do you happen have an idea on this? what solver do you use?
Thanks a lot for the advice. Turns out I have to use spf.sr for my definition. That brings the question, however, weather the single phase flow is a good assumption?
I get the the error: "Failed to find a solution for the initial parameter.
Maximum number of Newton iterations reached.
Returned solution is not converged."
I changed the settings in the solver but no luck. Maybe a two phase flow non-linear stationary solver is better choice? Do you happen have an idea on this? what solver do you use?