[Mohamad.Baassiri]

Dears,

I'm trying to load a simple UDF to mimic ideal gas density in Fluent (2023R1).

Fluent is crashing as soon as I run the simulation (floating point error). I'm using the below udf:

#include <udf.h>
#include <global.h>

/* The variables below need to be set for a particular gas */
/* CO2 */

#define RGASU UNIVERSAL_GAS_CONSTANT
#define MWT 44.01

/* REFERENCE STATE */

#define P_REF 101325
#define T_REF 288.15

DEFINE_PROPERTY(cell_density,c,t)

{
real rho;
real p;
real p_operating;
real T;

p_operating=RP_Get_Real("operating-pressure");
p=C_P(c,t);
T=C_T(c,t);
rho= (p+p_operating)/(RGASU*T/MWT);

return rho;
}

If I replace p and T by constant values, the solver works fine. The issue occurs only when I let p or T to be unknown (i.e. to be calculated by fluent). Anything wrong in the UDF? Any thoughts on this would be appreciated.

Thanks,

[AlexanderZ]

how to calculate pressure for your UDF if density is unknown for initial step?

[Mohamad.Baassiri]

Hi Alexander, thanks for your message.

Looking at the udf again, I have already defined the pressure initially. The problem as it appears to me is that I am not able to call the updated values in the UDF.

Best,