How to call mixture properties in a UDF
 

Hello,

I have a simple question. I am writing an UDF to calculate MIXTURE viscosity. But i need to call the MIXTURE DENSITY data somehow. Does anyone know how to include MIXTURE PROPERTIES in a UDF as a macro ? ( such as mixture density, mixture specific heat etc. )

Or, perhaps, does C_R(c,t) do exactly that ?

Also is it possible to call species critical properties into an UDF to use in mixture rule combinations ?

Thanks in advance.

Alper

Hi,

if you are using you get the mixture domain from adjust macro then you need to get the mixture thread and then loop through the cells in the thread. Something like this:
cheers!

Dear Sun,

I am using a real-gas model (not UDF, Redlich Kwong in FLUENT) for mixture density. Isn't there a way to simply call the cell mixture density ? Because with DEFINE_ADJUST, i would calculate a mixture property that is already calculated by FLUENT itself each time.

Am i wrong ?

Same thing also goes for mixture critical temperature, volume and constant volue specific heat too. There is no macro to call them from mixture domain to use directly ?

Best Regards.

Hi,

If I understand the question, you can probably export the solution data into any file formats that you'd like. File>Export>Solution data...

Also, take a look at this page.

Cheers!

No, exporting data once the solution is converged is not the problem. Problem is as follows :

* I am trying to simulate a real-gas reacting flow and trying to define a composition-dependent MIXTURE VISCOSITY via a UDF . (Chung et al. method)

* In order to do so, i need to obtain MIXTURE DENSITY somehow. Using DEFINE_ADJUST, as you suggested earlier, is an option but FLUENT already calculates the MIXTURE DENSITY by itself when i choose the real-gas model in mixture box.

I am simply trying to obtain the mixture density in each cell, that is calculated by FLUENT, to calculate the MIXTURE VISCOSITY. ( Mixture density is a parameter in the formulation )

I hope it is more clear now.

Can it be helped ? :)

Best Regards.

Have you tried something simple like this:
The idea is to see what value you are getting from the C_R(c,t) macro. Isn't it already the mixture density?

Hello Sun,

I used C_R(c,t) for mixture density and menage to compile the code successfully after spending a week for editing bugs. I think it will work fine because i double-checked the code with MATLAB to see if the values are in agreement with similar academic papers.

I will share the work once i validete it with an combustion case and share the results.

By the way, is there list for PROP_ values for mixture species ?

PROP_rho, PROP_mu, PROP_ktc and PROP_mwi are provided in the UDF Manual but i think critical properties for mixture species are accessible too.

Regards.

Glad to hear that everything worked out fine. :)
I am not sure if there is list for that. I usually use UDF manual to find out what macro I need. Looking forward to see the results
good luck!

same problem
 

Hello dear Refik
I have the same problem and i cant find pure and mixture density function for UDF. would you please help me?
thank you so much

Well C_R indeed returns the mixture density as explained earlier.

I assume by "pure" you mean species-density, for which you'll have to formulate a UDF.
But i reckon you have very little use for species-density if you are working with turbulent flow.

Udf
 

Thanks so much.
Would you please let me see your UDF ? Because i want to calculate mixture gas viscosity like you.
Best regards