[ndabir]

Hi,

I am trying to use a real gas fluid in my simulations. Therefore, I am using exactly the same udf example in Fluent help to try to understand how it works. So I exactly copy the code from manual in a .c file. Then I try to interpret the udf file. But I am not able to interpret the file. Every time I try to interpret the code, an error is shown:

line 15: parse error

Do you guys know if I can interpret a udf for real gases? Or just compiling the code is the only option?
Below is the code I am trying to interpret:


#include "udf.h"
#include "stdio.h"
#include "ctype.h"
#include "stdarg.h"

#define MW 28.966 /* molec. wt. for single gas (Kg/Kmol) */
#define RGAS (UNIVERSAL_GAS_CONSTANT/MW)

static int (*usersMessage)(char *,...);
static void (*usersError)(char *,...);


DEFINE_ON_DEMAND(I_do_nothing)
{
/* This is a dummy function to allow us to use */
/* the Compiled UDFs utility */
}


void IDEAL_error(int err, char *f, char *msg)
{
if (err)
usersError("IDEAL_error (%d) from function: %s\n%s\n",err,f,msg);
}

void IDEAL_Setup(Domain *domain, cxboolean vapor_phase, char *filename,
int (*messagefunc)(char *format, ...),
void (*errorfunc)(char *format, ...))
{
/* Use this function for any initialization or model setups*/
usersMessage = messagefunc;
usersError = errorfunc;
usersMessage("\nLoading Real-Ideal Library: %s\n", filename);
}

double IDEAL_density(double Temp, double press, double yi[])
{
double r = (press-506625.0)/(RGAS*Temp); /* Density at Temp & press */

return r; /* (Kg/m^3) */
}

double IDEAL_specific_heat(double Temp, double density, double P, double yi[])
{
double cp=1006.43;

return cp; /* (J/Kg/K) */
}

double IDEAL_enthalpy(double Temp, double density, double P, double yi[])
{
double h=Temp*IDEAL_specific_heat(Temp, density, P, yi);

return h; /* (J/Kg) */
}

#define TDatum 288.15
#define PDatum 1.01325e5

double IDEAL_entropy(double Temp, double density, double P, double yi[])
{
double s=IDEAL_specific_heat(Temp,density,P,yi)*log(fabs( Temp/TDatum))+
RGAS*log(fabs(PDatum/P));
return s; /* (J/Kg/K) */
}


double IDEAL_mw(double yi[])
{
return MW; /* (Kg/Kmol) */
}

double IDEAL_speed_of_sound(double Temp, double density, double P, double yi[])
{
double cp=IDEAL_specific_heat(Temp,density,P,yi);

return sqrt(Temp*cp*RGAS/(cp-RGAS)); /* m/s */
}

double IDEAL_viscosity(double Temp, double density, double P, double yi[])
{
double mu=1.7894e-05;

return mu; /* (Kg/m/s) */
}

double IDEAL_thermal_conductivity(double Temp, double density, double P,
double yi[])
{
double ktc=0.0242;

return ktc; /* W/m/K */
}

double IDEAL_rho_t(double Temp, double density, double P, double yi[])
{
/* derivative of rho wrt. Temp at constant p */
double rho_t=-density/Temp;

return rho_t; /* (Kg/m^3/K) */
}

double IDEAL_rho_p(double Temp, double density, double P, double yi[])
{
/* derivative of rho wrt. pressure at constant T */
double rho_p=1.0/(RGAS*Temp);

return rho_p; /* (Kg/m^3/Pa) */
}

double IDEAL_enthalpy_t(double Temp, double density, double P, double yi[])
{
/* derivative of enthalpy wrt. Temp at constant p */
return IDEAL_specific_heat(Temp, density, P, yi);
}


UDF_EXPORT RGAS_Functions RealGasFunctionList =
{
IDEAL_Setup, /* initialize */
IDEAL_density, /* density */
IDEAL_enthalpy, /* enthalpy */
IDEAL_entropy, /* entropy */
IDEAL_specific_heat, /* specific_heat */
IDEAL_mw, /* molecular_weight */
IDEAL_speed_of_sound, /* speed_of_sound */
IDEAL_viscosity, /* viscosity */
IDEAL_thermal_conductivity, /* thermal_conductivity */
IDEAL_rho_t, /* drho/dT |const p */
IDEAL_rho_p, /* drho/dp |const T */
IDEAL_enthalpy_t, /* dh/dT |const p */
IDEAL_enthalpy_p /* dh/dp |const T */
};

[pakk]

Since line 15 is around the place where it says this:

/*This is a dummy function to allow us to use */
/* the Compiled UDFs utility */

I would guess that this indeed needs to be compiled to work.

Take some time to get the compiler working. Interpreting functions in fluent has so many limitations, I think they should just remove the functionality...

[ndabir]

Thanks Pakk. That is something I was trying to avoid since you know how challenging is to make Fluent compile a code...

[pakk]

In fact I don't recognize that it is difficult to compile a code. Maybe I was lucky, but on my pc after everything was installed, it directly worked.

(I am not saying you are wrong; I have seen many questions about how to make compiling work, so clearly other people do have that experience.)