[denis.sanga@hotmail.it]

Good morning,
I need to pass the reference values from fluent scheme to udf. In particular I setted the reference values using

report/reference-values/compute/pressure-inlet

but I need of all parameters inside my UDF. Can someone help me to read them values from my udf? maybe is requested to save them in a rpvar list before?
thank you very much
Best Regards
Denis

[chienfm]

Hello Denis,

There are few ways to do that. My normally way is to use input parametric for udf. You can set up them in User define > Parameters > More > UDF > Select. In select parameter table, you can create your variable by choosing New Parameter. In here you can set its value and reference name. Click Ok when you finish an back to the "Use input Parameter for UDF" table, click "Define" to add your new variable, and then press Print to check your value. The Parameter should be called in UDF by RP_Get_Parameter("real-n"), where "real-n" is the ID of the variable you created (can check by Print)

Another way is to follow the steps here: https://www.computationalfluiddynami...sys-workbench/

I hope you find it useful.

Regards,
Chung.

[denis.sanga@hotmail.it]

Thank you really much for your answer and help. I'm sorry for another question. From your method I don't understand how to associate to some parameter the Reference values which fluent compute from some surface.
Or better: I would like to read from my udf the Reference values Area, Density, Length, Velocity, Temperature which are calculated automatically from some surface by Fluent.

Thank you really really much and I'm sorry for disturb
Best Regards
Denis

[chienfm]

Originally Posted by denis.sanga@hotmail.it

e.
Or better: I would like to read from my udf the Reference values Area, Density, Length, Velocity, Temperature which are calculated automatically from some surface by Fluent.

Hello Denis,

For that purpose, it really depends on your specific requirements. I assume you want to update reference values after each iteration, so you can use DEFINE_EXCUTE_AT_END function to calculate your parameters then pass back to your profile, source, property or any other function, just like a C program.

Regards,
Chung.

[denis.sanga@hotmail.it]

Thank you really really much again.
My purpose is to use that parameters to find dimensionless force and moment coefficients. For that I would read all the parameter calculated by the command

report/reference-values/compute/pressure-inlet

by the udf. For this time I'm not interested in change that values but just use them. Maybe have you an example to reach that values by udf functions?

Many many thanks
Best Regars
Denis

[obscureed]

Hi Denis,

I'm familiar with the Reference Length, Area etc, as set in Reference Values. One way to deal with these is to set Length=1.0m, Area=1.0m2, viscosity=1.0Pa.s, and so on, and then you can almost forget that they exist. (You might want more sensible values in some variables: Temperature and Ratio of Specific Heats.)

I think you will find that those reference values are available as RP variables, so in a UDF you should be able to access them via something like this:

  real ref_pressure;
  ref_pressure = RP_Get_Real("reference-pressure")

In parallel, I might recommend being a bit careful (but I'm not sure it's needed):

  real ref_pressure,ref_length,ref_density,ref_area;

#if !RP_NODE
  ref_pressure = RP_Get_Real("reference-pressure")
  ref_length = RP_Get_Real("reference-length")
  ref_density = RP_Get_Real("reference-density")
  ref_area = RP_Get_Real("reference-area")
#endif
  host_to_node_real_4(ref_pressure,ref_length,ref_density,ref_area);

If things get really bad, remember there is always

if(RP_Variable_Exists_P("varname") ...

You can find the names of these RP-variables by opening up the .cas file from a small test-case in a good text editor.



I'm not at all familiar with the parameters returned by the TUI command that you mentioned. Please can you explain how/where they are used?

By the way, you are correct in not assuming write-access even when a variable is available in a UDF.

Good luck!
Ed