[sooraj546]

#include "udf.h"
#include "mem.h"

DEFINE_SPECIFIC_HEAT(iron_sp, Tf, Cp, c, t)
{

Tf = C_T(c,t);
if (Tf<800)
{
Cp= 14.379+(49.006*Tf/1000)+(-57.471*Tf*Tf/1000000)+(41.243*Tf*Tf*Tf/1000000000);
}
else if (Tf>=800 && Tf<1000)
{
Cp= 213.76+(-460.596*Tf/1000)+(301.135*Tf*Tf/1000000);
}
else if (Tf>=1000 && Tf<1040)
{
Cp= 8759.86+(-17497.2*Tf/1000)+(8773.75*Tf*Tf/1000000);
}
else if (Tf>=1040 && Tf<1042)
{
Cp= -6415.79+(6237.5*Tf/1000);
}
else if (Tf>=1042 && Tf<1060)
{
Cp= 124237.633+(-234458.544*Tf/1000)+(110661.111*Tf*Tf/1000000);
}
else if (Tf>=1060 && Tf<1184)
{
Cp= 542.908+(-816.002*Tf/1000)+(331.482*Tf*Tf/1000000);
}
else
{
Cp= 24.036+(8.295*Tf/1000)+(0.022*Tf*Tf/1000000);
}
return Cp;
}




i am getting an error saying "error C2223: left of '->storage' must point to struct/union" for line 7 i.e. Tf = C_T(c,t);
i know this is a declaration error but still i am not able to resolve it, Kindly help me out

[obscureed]

Hi sooraj546,

Are you using the correct syntax for DEFINE_SPECIFIC_HEAT? What version of Fluent is this?

Good luck!
Ed

[sooraj546]

Originally Posted by obscureed

Hi sooraj546,

Are you using the correct syntax for DEFINE_SPECIFIC_HEAT? What version of Fluent is this?

Good luck!
Ed

thanks a lot for replying .................i have given the link of the UDF , I am currently using fluent 18.0

https://www.sharcnet.ca/Software/Ans...e_sp_heat.html

[moh_zain]

HI you need to define this C_T is it real or later or what just or delete line 7 and the code is also will be fine

[AlexanderZ]

for v18.0 specific heat macro:

DEFINE_SPECIFIC_HEAT (name,T,Tref,h,yi)

example

/**********************************************************************
UDF that computes specific heat and sets the sensible enthalpy
to the referenced value
***********************************************************************/
#include "udf.h"
DEFINE_SPECIFIC_HEAT(my_user_cp, T, Tref, h, yi)
{
real cp=2000.;
*h = cp*(T-Tref);
return cp;
}

more details in Ansys Fluent Customization manual

best regards

[sooraj546]

Originally Posted by AlexanderZ

for v18.0 specific heat macro:

DEFINE_SPECIFIC_HEAT (name,T,Tref,h,yi)

example

/**********************************************************************
UDF that computes specific heat and sets the sensible enthalpy
to the referenced value
***********************************************************************/
#include "udf.h"
DEFINE_SPECIFIC_HEAT(my_user_cp, T, Tref, h, yi)
{
real cp=2000.;
*h = cp*(T-Tref);
return cp;
}

more details in Ansys Fluent Customization manual

best regards

I have shared this link above as well. Thanks lot for replying still can u give me som suggestions how to rectify that error

[sooraj546]

Originally Posted by moh_zain

HI you need to define this C_T is it real or later or what just or delete line 7 and the code is also will be fine

C_T is the macro for getting temperature at each cell along the thread I needed it else this code is meaningless

Thanks a lot for replying,

[AlexanderZ]

/**********************************************************************
UDF that computes specific heat and sets the sensible enthalpy
to the referenced value
***********************************************************************/
#include "udf.h"
DEFINE_SPECIFIC_HEAT(my_user_cp, Tf, Tref, h, yi)
{
real Cp;
if (Tf<800)
{
Cp= 14.379+(49.006*Tf/1000)+(-57.471*Tf*Tf/1000000)+(41.243*Tf*Tf*Tf/1000000000);
}
else if (Tf>=800 && Tf<1000)
{
Cp= 213.76+(-460.596*Tf/1000)+(301.135*Tf*Tf/1000000);
}
else if (Tf>=1000 && Tf<1040)
{
Cp= 8759.86+(-17497.2*Tf/1000)+(8773.75*Tf*Tf/1000000);
}
else if (Tf>=1040 && Tf<1042)
{
Cp= -6415.79+(6237.5*Tf/1000);
}
else if (Tf>=1042 && Tf<1060)
{
Cp= 124237.633+(-234458.544*Tf/1000)+(110661.111*Tf*Tf/1000000);
}
else if (Tf>=1060 && Tf<1184)
{
Cp= 542.908+(-816.002*Tf/1000)+(331.482*Tf*Tf/1000000);
}
else
{
Cp= 24.036+(8.295*Tf/1000)+(0.022*Tf*Tf/1000000);
}
*h = Cp*(Tf-Tref);
return cp;
}

best regards

[sooraj546]

Originally Posted by AlexanderZ

/**********************************************************************
UDF that computes specific heat and sets the sensible enthalpy
to the referenced value
***********************************************************************/
#include "udf.h"
DEFINE_SPECIFIC_HEAT(my_user_cp, Tf, Tref, h, yi)
{
real Cp;
if (Tf<800)
{
Cp= 14.379+(49.006*Tf/1000)+(-57.471*Tf*Tf/1000000)+(41.243*Tf*Tf*Tf/1000000000);
}
else if (Tf>=800 && Tf<1000)
{
Cp= 213.76+(-460.596*Tf/1000)+(301.135*Tf*Tf/1000000);
}
else if (Tf>=1000 && Tf<1040)
{
Cp= 8759.86+(-17497.2*Tf/1000)+(8773.75*Tf*Tf/1000000);
}
else if (Tf>=1040 && Tf<1042)
{
Cp= -6415.79+(6237.5*Tf/1000);
}
else if (Tf>=1042 && Tf<1060)
{
Cp= 124237.633+(-234458.544*Tf/1000)+(110661.111*Tf*Tf/1000000);
}
else if (Tf>=1060 && Tf<1184)
{
Cp= 542.908+(-816.002*Tf/1000)+(331.482*Tf*Tf/1000000);
}
else
{
Cp= 24.036+(8.295*Tf/1000)+(0.022*Tf*Tf/1000000);
}
*h = Cp*(Tf-Tref);
return cp;
}

best regards

this code will work sir fine, but my intention is to obtain temperature of each control volume at each iteration and use it for Cp calculation, Thats y i have specified Tf = C_T(c,t) .............if i use here Tf the fluent database will never know its the temperature depending on the control volume ..............am i right sir?

Once again thanks a lot for replying.....................!

[AlexanderZ]

read macro header

DEFINE_SPECIFIC_HEAT(my_user_cp, Tf, Tref, h, yi)

Tf here (was T) is temperature of cell, it is provided automatically. You do not need to redefine it
test this code, initialize your case with different temperatures and check Cp. Sounds easy

By the way, change very last line
was

return cp;

to be

return Cp;

best regards

[sooraj546]

thanks a lot for your reply ...........it really helped me out.