Glass viscosity
 

Hello,
I would like to simulate the glass forming with a VOF model. As the viscosity of the glass varies strongly with the temperature, I would know how to implement a viscosity law with the temperature in CFX Pre (I already have this relationship).
Thank you very much

You simply define the viscosity as a function and put that in your material model. You can define the function with interpolation tables, CEL expressions or user fortran. For examples of how to do these things and how to modify material models look in the CFX tutorials.

Cel
 

So is it possible to set a CEL expression like a polynomial with the temperaure as variable for the viscosity material property?

Yes that is possible. I would recommend to limit temperature using min & max functions, to avoid unrealistic viscosities outside the range of applicability during the simulation.
Use the Evaluation-fucntion of CFX-Pre when setting up the expression. This allows you to check whether you get realistic values and do not make a typo.
Also, make sure you use enough digitis for your polynomocal coefficients a,b,c, etc. Round off errors can become large if you have a term like a*T^6
In other words: check, check, double check.

Min max
 

Thank you, how can I limit the function? Can you write an sample?

Min function
 

Thank you, how can I limit the function? Can you write an sample?

Have a look in the CFX reference guide for functions available in CEL. Functions which can be used as limiters include step, if and max/min.

min(1e7[Pa s], max(1 [Pa s], function))


where function is your viscosity as function of whatever you want.
If you use one of the predefined viscosity functions like powerlow or Hershel-Bukly, min and max values for shear rate are available as well.


As Glenn mentioned, look for it in the manual.

Thank
 

Thank you very much.