Learning Forum

[khalidb77]

Dear FLUENT users,

I used the below UDF for specific heat in terms of liquid fraction it compiled normally and uploaded successfully into Cp in materials panel but an error happened and the program quit with unknown reason as soon as I initial the solution? knowing that I activated the melting and solidification model and the case is running normally without using the UDF? So is there an error on it? any recommendations are appreciated please?

#include "udf.h"
/*
#define cps 1800.0
#define cpl 2400.0
#define lat 160000.0
*/
DEFINE_SPECIFIC_HEAT(specificheat, T, Tref, h, yi)
{
real cpm,dt;
Tref=308;
real cps = 1800.0;
real cpl = 2400.0;
real lat = 160000.0;
Thread *t;
cell_t c;

dt=exp(-T*(T-Tref)*(T-Tref)/4.0)/sqrt(4.0*3.14);

cpm =cps+(cpl-cps)*C_LIQF(c,t)+lat*dt;

*h = cpm*(T-Tref);
return cpm;

}

 

[DrAmine]

That would not work: There is no way to access cell and thread data from within the DEFINE_SPECIFIC_HEAT macro.

[khalidb77]

Thanks Amine for the reply. So how I can resolve the error? is there any changes can I make within the UDF?

 

Khalid

[DrAmine]

One way via udrgm (not tested).

[khalidb77]

Excuse me what did you mean with udrgm?

[DrAmine]

User defined real gas model.

[khalidb77]

But I do not have a gas in my case? I used PCM model hence I have just two liquids and a solid?

[DrAmine]

Can be used for liquid eos. Only way to make the trick. Or you use solidification and melting model or you use specie transport and code Cp with mass fraction. The problem here is that the macro to modify cp dies not support cell access or cell loop just temperature access and species access.

[khalidb77]

I am actually used the solidification and melting model? then is there a solution to the problem?

[DrAmine]

Just provide Cp as temperature dependent and melt heat in the material panel.

[khalidb77]

The problem Cp is function of liquid fraction too? OK I need to ask is it possible to define LIQF inside the specific heat UDF using the definition below (where f(T) is LIQF):

Then I give the relation of Cp as written on the UDF in my first post?

[DrAmine]

Please look thoroughly in my answers and you will see that Cp can be defined in UDF for temperature dependency.

[khalidb77]

I thought you never notice what I mentioned in my previous post. If you see the definition at the picture I sent you will realized that LIQF is a function of temperature too. Hence can I use this definition for f(T) (liquid fraction) inside the specific heat UDF or no?

 

Thanks

Khalid

[DrAmine]

Again: You cannot access any cell variables in DEFINE_SPECIF_HEAT you need to use the passed temperature and species arguments into the macro.