Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Non-Newtonian models in COMSOL

Seyed Mohammad Javid Mahmoudzadeh Akherat

Please login with a confirmed email address before reporting spam

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?

2 Replies Last Post Jan 7, 2015, 7:10 p.m. EST

Please login with a confirmed email address before reporting spam

Posted: 10 years ago Jan 7, 2015, 8:00 a.m. EST
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


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


Seyed Mohammad Javid Mahmoudzadeh Akherat

Please login with a confirmed email address before reporting spam

Posted: 10 years ago Jan 7, 2015, 7:10 p.m. EST
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?
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?

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.