Modelling Bingham in CFX 11.0
 

Hi!

I'm trying to implement a Bingham-Material by using CCL as follows:

LIBRARY: MATERIAL: MRF ANSYS Material Group = User Option = Pure Substance Thermodynamic State = Liquid

PROPERTIES:

Option = General Material

DYNAMIC VISCOSITY:

Option = Bingham

Yield Stress = 50000 [kg m^-1 s^-2]

Viscosity Consistency = 0.5 [kg m^-1 s^-1]

Minimum Shear Strain Rate = 1.0E-3 [s^-1]

Maximum Shear Strain Rate = 100 [s^-1] END

EQUATION OF STATE:

Density = 4500 [kg m^-3]

Molar Mass = 1.0 [kg kmol^-1]

Option = Value END

END END

It doesn't work and I get the following error message:

"The parameter "Option in "/LIBRARY/MATERIAL:MRF ANSYS/PROPERTIES/DYNAMIC VISCOSITY" has the value "Bingham". This does not match any of the allowed values: "Value, Sutherlands Formula, Rigid Non Interacting Sphere Model"."

As I understand this error message, the Bingham-Modell is not known by the program, but in the help it is explained in that way. Is there something wrong in my CCL-command?

I'm using ANSYS Workbench with CFX V11.0 SP1!

Hopefully someone can help me. I look forward.

Dirk

Re: Modelling Bingham in CFX 11.0
 

As I understand, Bingham fluid can not be recognized by CFX. You can not enable this function beyond the program...

Re: Modelling Bingham in CFX 11.0
 

I found this in the ANSYS Knowledgebase:

#463622 - Non-Newtonian Fluids in ANSYS CFX Product: CFX Version: 10.0 Category: CFX GENERAL File(s) Available for Download: 463622

Q: I would like to set-up a problem for a fluid with a non-Newtonian viscosity dependence. Are there any built in models for doing this in CFX?

A: There are various non-Newtonian viscosity models available in CFX as beta features. The available models are the Herschel-Bulkley, Bird-Carreau, Cross, and Power-Law models. The Bingham Plastic model can be set up as a special case of the Herschel-Bulkley model. To enable access to the models, you can modify the RULES file located in the /etc folder of the CFX installation directory as follows. 1. First copy the existing RULES file to another file (say RULES.OLD) so that the original file is preserved. 2. Edit the RULEs file and find the object: SINGLETON: DYNAMIC VISCOSITY Replace the entire SINGLETON: DYNAMIC VISCOSITY object with the corresponding object contained in the attached file short_rules. 3. Save the modified RULES file and start the CFX launcher. If you edit an existing definition file using the Solver Manager, you will be able to change the Option for Dynamic Viscosity for a particular material to one of the non-Newtonian options. You must then add and set the desired parameters for that particular model. Contact your CFX support representative if you have any questions on this procedure.

Has anyone tried to enable Bingham fluid or other non-Newton by following this instruction?? I can't get it working... Is it only working in CFX 10.0 ?? Would be curious, if it is working in 10.0 but not in 11.0.

Re: Modelling Bingham in CFX 11.0
 

Dirk,

The option should be "Herschel-Bulkley" other than "Bingham" if it works. It may be still invalid because I did not test this feature. If you have any question on this, you can contact CFX support. I think it is the most efficient way to get through this.

Rikio

Re: Modelling Bingham in CFX 11.0
 

Dear Dirk,

i also have the same problem just like you and because of your questions, i learn smth. more about this topic in cfx. i did not find a solution for our problem, but i want to show, what i have done.

1. i look in the help of cfx-pre (search hidden feature) --> under option you can select "enable beta features". with this you should see the beta features (but i don´t see anything)

and

2. my material

MATERIAL: Gemenge

Material Description = Gemenge

Material Group = User

Option = Pure Substance

Thermodynamic State = Liquid

PROPERTIES:

Option = General Material

DYNAMIC VISCOSITY:

Option = Herschel Bulkley

Yield Stress = 50000 [kg m^-1 s^-2]

Viscosity Consistency = 0.5 [kg m^-1 s^-1]

Power Law Index = 1

Minimum Shear Strain Rate = 1.0E-3 [s^-1]

Maximum Shear Strain Rate = 100 [s^-1]

END

EQUATION OF STATE:

Density = 4500 [kg m^-3]

Molar Mass = 1.0 [kg kmol^-1]

Option = Value

END

SPECIFIC HEAT CAPACITY:

Option = Value

Specific Heat Capacity = 2080.1 [J kg^-1 K^-1]

Specific Heat Type = Constant Volume

END

THERMAL CONDUCTIVITY:

Option = Value

Thermal Conductivity = 2 [W m^-1 K^-1] END

During i used this in cfx, the programm also told me, that i have to use a power law index. so i think the programm have to know this option.

best regards sven

Re: Modelling Bingham in CFX 11.0
 

Yes, I had already activated that option for hidden functions. But I get the following error message anyway, if I try to implement a Bingham-fluid or a Heschel-Bulkley-fluid by using CCL:

The parameter "Option in "/LIBRARY/MATERIAL:MRF50KHB/PROPERTIES/DYNAMIC VISCOSITY" has the value "Herschel Bulkley". This does not match any of the allowed values: "Value, Sutherlands Formula, Rigid Non Interacting Sphere Model".

The HB-fluid is shown in the tree, but I can't choose it for my simulation.

In the meantime I have spoken to our local CFX distributor. Implementing models like Bingham or Herschel-Bulkley is not yet support, it could work fine, but they don't advise to use it. The better way is the work with the apparent viscosity. In the near future ANSYS CFX 12 will be released and then these functions will be activated.

Re: Modelling Bingham in CFX 11.0
 

Dear Dirk,

please look to this page

http://pubs.acs.org/doi/full/10.1021/ie800496x

equation 1 show the herschel-bulkley model and if you combine the solution in the tutorial manual (Non-Newtonian Fluid flow in an annulus), then i think this should work.