[erginbayrak]

Hi, I take a compiled error from my code as follows;

supercritical_cp.c
..\..\src\supercritical_cp.c(3): error C2065: 'real': undeclared identifier
..\..\src\supercritical_cp.c(3): error C2146: syntax error: missing ';' before identifier 'cp'
..\..\src\supercritical_cp.c(3): error C2065: 'cp': undeclared identifier
..\..\src\supercritical_cp.c(7): error C2065: 'cp': undeclared identifier
..\..\src\supercritical_cp.c(11): error C2065: 'cp': undeclared identifier
..\..\src\supercritical_cp.c(15): error C2065: 'cp': undeclared identifier
..\..\src\supercritical_cp.c(19): error C2065: 'cp': undeclared identifier
..\..\src\supercritical_cp.c(21): error C2100: illegal indirection
..\..\src\supercritical_cp.c(21): error C2065: 'cp': undeclared identifier
..\..\src\supercritical_cp.c(22): error C2065: 'cp': undeclared identifier

Done.

My code is;

DEFINE_SPECIFIC_HEAT(supercritical_cp, T, Tref, h, yi)
{
real cp;

if (306. >= T >= 285.)
{
cp = 0.0029 * pow(T, 6.) - 5.0805 * pow(T, 5.) + 3733.1 * pow(T, 4.) - 1e+6 * pow(T, 3.) + 3e+8 * pow(T, 2.) - 4e+10 * T + 2e+12;
}
if (307.8 >= T > 306.)
{
cp = 2342.3 * pow(T, 6.) - 4e+6 * pow(T, 5.) + 3e+9 * pow(T, 4.) - 1e+12 * pow(T, 3.) + 3e+14 * pow(T, 2.) - 4e+16 * T + 2e+18;
}
if (310. >= T > 307.8)
{
cp = -4663.3 * pow(T, 6.) + 9e+6 * pow(T, 5.) - 7e+9 * pow(T, 4.) + 3e+12 * pow(T, 3.) - 6e+14 * pow(T, 2.) + 8e+16 * T - 4e+18;
}
if (350. >= T > 310.)
{
cp = 8e-5 * pow(T, 6.) - 0.1631 * pow(T, 5.) + 135.66 * pow(T, 4.) - 60154 * pow(T, 3.) + 1e+7 * pow(T, 2.) - 2e+9 * T + 1e+11;
}
*h = cp*(T-Tref);
return cp;
}

I would like to be grateful if you could say your recommendations.
Regards,

[naffrancois]

Hello,

Could it be that you forgot to include udf.h or that it can't be located ?

edit: probably unrelated to your error but what happens to cp if T does not lie in [306,350] ? You should consider default values when using if statements.

[erginbayrak]

Originally Posted by naffrancois

Hello,

Could it be that you forgot to include udf.h or that it can't be located ?

edit: probably unrelated to your error but what happens to cp if T does not lie in [306,350] ? You should consider default values when using if statements.

Hello, thank you for your reply. I forgot udf.h. I am trying to catch a sharp increase of specific heat in the vicinity of the near-critical region of CO2. My revised code is working (there is no problem with compiling) but after the user defining of thermophysical properties for CO2, I have taken another error as follows:

My Code
#include "udf.h"

DEFINE_SPECIFIC_HEAT(supercritical_cp2, T, Tref, h, yi)
{
real cp;

if (285. > T)
{
cp = 2540.85;
}
if (306. >= T >= 285.)
{
cp = 0.0029 * pow(T, 6.) - 5.0805 * pow(T, 5.) + 3733.1 * pow(T, 4.) - 1e+6 * pow(T, 3.) + 3e+8 * pow(T, 2.) - 4e+10 * T + 2e+12;
}
if (307.8 >= T > 306.)
{
cp = 2342.3 * pow(T, 6) - 4e+6 * pow(T, 5) + 3e+9 * pow(T, 4) - 1e+12 * pow(T, 3) + 3e+14 * pow(T, 2) - 4e+16 * T + 2e+18;
}
if (310. >= T > 307.8)
{
cp = -4663.3 * pow(T, 6) + 9e+6 * pow(T, 5) - 7e+9 * pow(T, 4) + 3e+12 * pow(T, 3) - 6e+14 * pow(T, 2) + 8e+16 * T - 4e+18;
}
if (350. >= T > 310.)
{
cp = 8e-5 * pow(T, 6) - 0.1631 * pow(T, 5) + 135.66 * pow(T, 4) - 60154. * pow(T, 3) + 1e+7 * pow(T, 2) - 2e+9 * T + 1e+11;
}

if (T > 350.)
{
cp = 1546.34;
}
*h = cp*(T-Tref);
return cp;
}

Error:

WARNING: Invalid cp (0.000000e+00 J/kgK) for carbon-dioxide at temperature 289.692000 K
iter continuity x-velocity y-velocity energy k omega intermit retheta time/iter
Stabilizing pressure coupled to enhance linear solver robustness.
Stabilizing pressure coupled using GMRES to enhance linear solver robustness.

Experiencing convergence difficulties - temporarily relaxing and trying aga

ivergence detected in AMG solver: pressure coupled Stabilizing k to enhance linear solver robustness.
Stabilizing k using GMRES to enhance linear solver robustness.
Divergence detected in AMG solver: pressure coupled
Divergence detected in AMG solver: k
Divergence detected in AMG solver: omega
Divergence detected in AMG solver: intermit
Divergence detected in AMG solver: retheta
Divergence detected in AMG solver: temperature

WARNING: Invalid cp (0.0000Error at Node 0: floating point exception
Error at Node 1: floating point exception
Error at Node 2: floating point exception
Error at Node 3: floating point exception
00e+00 J/kgK) for carbon-dioxide at temperature 289.692000 K

Error at Node 4: floating point exception
Error at Node 5: floating point exception
Error at Node 6: floating point exception
Error at Node 7: floating point exception
Error at Node 8: floating point exception

Error at host: floating point exception
Error at Node 9: floating point exception
Error at Node 10: floating point exception
Error at Node 11: floating point exception

Error: floating point exception
Error Object: #f

[naffrancois]

Hello,

I don't have experience with fluent so I can just provide very general help here.

If I were you I would double check first the correlations you are using by plotting them for each temperature range. Hand computing your correlation at T=289.692K gives an unrealistic value for cp ~ 10^12