[c_023]

Hello,

I have been Looking for a solution to this Problem across this Forum but did not find anything helpful. I wrote a User Defined Real Gas Model and want to compile this UDF. When Compiling, Fluent Returns the following error:
'error C2223: left of "->storage" must point to struct/union'
I get the error for every line where I have the following Code:
double PP = C_P(c,t);

is it not possible to declare and assign a local variable in that way inside something like this:

double_RGP_density(c,t)
{
double PP = C_P(c,t);
…
}

inside a UDRGM UDF?

I also tried declaring and then assigning, like this:
double PP;
PP = C_P(c,t);
buit this also yields an error…

Has anyone experienced the same compilation error?

Thanks in advance

[AlexanderZ]

pp is reserved name use my_pp for instance

[c_023]

Originally Posted by AlexanderZ

pp is reserved name use my_pp for instance

Thanks for the answer. I changed PP to MY_PP but the error is still the same. Is there Maybe a certain header I need to include for C_P(c,t) to work?
So far, I included the following:
#include "udf.h"
#include "stdio.h"
#include "ctype.h"
#include "stdarg.h"
#include "mem.h"
#include "arrays.h"

[AlexanderZ]

show your code

replace double type with real and run case in double precision

[c_023]

Originally Posted by AlexanderZ

show your code

replace double type with real and run case in double precision

my Code:

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

#define numPressure 100
#define numTemp 100

#define MW 28.96546
#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 RGP_error(int err, char *f, char *msg)
{
if (err)
usersError("Real_error (%d) from function: %s\n%s\n",err,f,msg);
}

void RGP_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 Library: %s\n", filename);
}


double RGP_density(c,t)
{

int iP;
int iT;
double P[numPressure];
double T[numTemp];
double RHO[numPressure][numTemp];
double T1;
double T2;
double P1;
double P2;
double MY_PP = C_P(c,t);
double MY_TT = C_T(c,t);
double RHO11;
double RHO12;
double RHO21;
double RHO22;
double T2T1;
double P2P1;
double P2MY_PP;
double MY_PPP1;
double MY_TTT1;
double T2MY_TT;
double interpRHO;
double R1;
double R2;

FILE *Tfile;
FILE *Pfile;
FILE *RHOfile;
Tfile = fopen("Tstruct.csv","r");
Pfile = fopen("Pstruct.csv","r");
RHOfile = fopen("RHOstruct.csv","r");

int counter1 = 0;
float buffer;
while (counter1 < numPressure)
{
fscanf(Pfile,"%f",&buffer);
P[counter1] = buffer;
counter1 += 1;
}
int counter2 = 0;
while (counter2 < numTemp)
{
fscanf(Tfile,"%f",&buffer);
T[counter2] = buffer;
counter2 += 1;
}
int counterP = 0;
int counterT = 0;

for (counterP = 0; counterP < numPressure; ++counterP)
{
for (counterT = 0; counterT < numTemp; ++counterT)
{
fscanf(RHOfile,"%f,",&buffer);
RHO[counterP][counterT] = buffer;
}

}

for (iP = 0; iP < numPressure; ++iP)
{
if (MY_PP <= P[iP] && MY_PP >= P[iP-1])
{
for (iT = 0; iT < numTemp; ++iT)
{
if (MY_TT <= T[iT] && MY_TT >= T[iT-1])
{
T1 = T[iT - 1];
T2 = T[iT];
P1 = P[iP - 1];
P2 = P[iP];
RHO11 = RHO[iP - 1][iT - 1];
RHO12 = RHO[iP - 1][iT];
RHO21 = RHO[iP][iT - 1];
RHO22 = RHO[iP][iT];
break;
}
}
}
}

T2T1 = T2 - T1;
P2P1 = P2 - P1;
T2MY_TT = T2 - MY_TT;
P2MY_PP = P2 - MY_PP;
MY_PPP1 = MY_PP - P1;
MY_TTT1 = MY_TT - T1;

interpRHO = 1.0 / (P2P1 * T2T1) * (
RHO11 * P2MY_PP * T2MY_TT +
RHO21 * MY_PPP1 * T2MY_TT +
RHO12 * P2MY_PP * MY_TTT1 +
RHO22 * MY_PPP1 * MY_TTT1
);

return interpRHO;

fclose(Tfile);
fclose(Pfile);
fclose(RHOfile);

}


[then the same for all other properties, and in the end:]

UDF_EXPORT RGAS_Functions RealGasFunctionList =
{
RGP_Setup, /* initialize */
RGP_density, /* density */
RGP_enthalpy, /* enthalpy */
RGP_entropy, /* entropy */
RGP_specific_heat, /* specific_heat */
RGP_mw, /* molecular_weight */
RGP_speed_of_sound, /* speed_of_sound */
RGP_viscosity, /* viscosity */
RGP_thermal_conductivity, /* thermal_conductivity */
RGP_rho_t, /* drho/dT |const p */
RGP_rho_p, /* drho/dp |const T */
RGP_enthalpy_t, /* dh/dT |const p */
RGP_enthalpy_p /* dh/dp |const T */
};




"Tstruct.csv" and "Pstruct.csv" are 1D-arrays with pressure and temperature Points, "RHOstruct.csv" is a 2D-array with Density[i,j] corresponding to the P[i] and T[j] Pressure and Temperature. The UDF takes the Pressure and Temperature and performs bilinear Interpolation to return the Density (and all other properties which i excluded because it is >1000 lines of Code.
The Code works well when just used within a C-Compiler without the UDF-specific commands. I know the Code will be very slow but this is not an issue as it will only be called once to create lookup tables.

P.S. I tried changing "double" to "real" and run in double precision but the error message stays the same...

[AlexanderZ]

function names are define wrong
was
double RGP_density(c,t)
to be
double RGP_density(cell_t c,Thread *t)

also all variables should be define in the top all function, for instance this will be a problem:
int counter2 = 0;
to be
int counter2;
counter2 = 0;

[c_023]

Originally Posted by AlexanderZ

function names are define wrong
was
double RGP_density(c,t)
to be
double RGP_density(cell_t c,Thread *t)

also all variables should be define in the top all function, for instance this will be a problem:
int counter2 = 0;
to be
int counter2;
counter2 = 0;

Thanks for the help, with your tips I got rid of the C2223 error. Now a bunch of new Errors turned up, like "C2081: "Thread": Name is not valid". I'll try to fix the Errors and will post the working Code if I get it to work.

[c_023]

Originally Posted by AlexanderZ

function names are define wrong
was
double RGP_density(c,t)
to be
double RGP_density(cell_t c,Thread *t)

This solution that you pointed out worked for me. The Code compiled now without Errors. The remaining Errors were just typos. Thanks again for the help.

[djamila77]

hi all ,

I need you help please , my question is:

How plotting a curve as a function of time on fluent in the steady case?

Thanks

[AlexanderZ]

Originally Posted by djamila77

hi all ,

I need you help please , my question is:

How plotting a curve as a function of time on fluent in the steady case?

Thanks

in steady case there is no time, that's why it has name steady