[sahoo]

I am getting the following error :-
..\..\src\tegtr.c(22): error C2143: syntax error: missing ';' before '{'

for following code :-

#include "udf.h"
#include "math.h"

enum
{
teg,
N_REQUIRED_UDS
};

DEFINE_DIFFUSIVITY(teg_diffusivity, cell, thread, i)
{

Thread *t;
cell_t c;
face_t f;

begin_c_loop (c,t)
{
real T;
T = C_T(c,t);
real rho_function(real T)
{
return -3.982*pow(10,-5) + 2.98*pow(10,-7)*T - 4.685*pow(10,-10)*pow(T,2) + 2.51*pow(10,-12)*pow(T,3) ;
}
C_UDSI(c,t,teg) = rho_function(C_T(c,t))*C_T_G(c,t)[0];
}
end_c_loop (c,t)
real T;
T = C_T(cell, thread);
return 1/C_UDSI(cell, thread,teg);
}

But I don't think, there is any error in line 22.
I have also tried to solve the error following this link :-
what is syntax error : missing ')' before ';'

But it didn't work. Any suggestions will be greatly appreciated.
Thank you

[`e`]

Your code has a definition for rho_function within the cell loop; this definition should be moved above the DEFINE_DIFFUSIVITY call. Also, these lines of code are redundant (not used):

real T;
T = C_T(c,t);
...
real T;
T = C_T(cell, thread);

as the temperature is directly called into rho_function with C_T. Lastly, variables should be declared at the beginning of a code block (for compliance with the programming language, ANSI C), and numbers should have a trailing dot to indicate that the value is a real number (to avoid erroneous typecasting).

[sahoo]

Thank you, it worked

[sahoo]

Is it necessary to define the rho_function() inside the loop?
Because without the loop I don't get any error but with the loop I am getting the following error:-
..\..\src\tegtr.c(10): error C2449: found '{' at file scope (missing function header?)
..\..\src\tegtr.c(18): error C2059: syntax error: '}'

for the following code:-

#include "udf.h"
#include "math.h"

enum
{
teg,
N_REQUIRED_UDS
};

begin_c_loop (c,t)
{
real rho_function(real T)
{
return -3.982*pow(10.,-5.) + 2.98*pow(10.,-7.)*T - 4.685*pow(10.,-10.)*pow(T,2.) + 2.51*pow(10.,-12.)*pow(T,3.) ;
}
C_UDSI(c,t,teg) = rho_function(C_T(c,t));
}
end_c_loop (c,t)

DEFINE_DIFFUSIVITY(teg_diffusivity, cell, thread, i)
{
Thread *t;
cell_t c;
face_t f;
return 1/C_UDSI(cell, thread,teg);
}

[`e`]

The functions should be defined outside of the loops and other functions. Remember that we can use 1.e-3 instead of calling pow(10,-3); improving readability and slightly reducing the compute time. Similarly, if the power is an integer, then expanding the power expression is the standard approach.

The DEFINE_DIFFUSIVITY macro is called for each cell (check the UDF manual for the description), and therefore you do not use the cell loop. The trailing dot is especially important for divisions such as 1/x. Here is the corrected code:

#include "udf.h"
#include "math.h"

enum
{
	teg,
	N_REQUIRED_UDS
};

real rho_function(real T)
{
	return -3.982e-5 + 2.98e-7*T - 4.685e-10*T*T + 2.51e-12*T*T*T;
}

DEFINE_DIFFUSIVITY(teg_diffusivity, c, t, i)
{
	C_UDSI(c,t,teg) = rho_function(C_T(c,t));
	return 1./C_UDSI(c,t,teg);
}

Although, are you sure you want to set the UDS values within the DEFINE_DIFFUSIVITY macro? Perhaps take a step back and think about what equations you are solving and which functions / macros need to be hooked into Fluent.

[sahoo]

Thanks Mr. 'e' your advice always works.
Actually I am solving the following equation:-
∇V= -α(T)∇T-ρ(T)J

for which 2 UDS are as follows:-

#include "udf.h"
#include "math.h"

enum
{
teg,
N_REQUIRED_UDS
};

real rho_function(real T)
{
return -3.982e-5 + 2.98e-7*T - 4.685e-10*T*T + 2.51e-12*T*T*T;
}

DEFINE_DIFFUSIVITY(teg_diffusivity, c, t, i)
{
C_UDSI(c,t,teg) = rho_function(C_T(c,t));
return 1./C_UDSI(c,t,teg);
}

#include "udf.h"
#include "math.h"

enum
{
teg1,
N_REQUIRED_UDS
};

real alpha_function(real T)
{
return 8.439e-4 - 3.81e-6*T + 6.736e-9*pow(T,-9.) - 3.934e-12*pow(T,-12.);
}

DEFINE_SOURCE(teg1_source, c, t, dS, eqn)
{
real T = C_T(c,t);
C_UDSI(c,t,teg1) = alpha_function(C_T(c,t))*C_T_G(c,t)[0];
dS[eqn] = C_UDSI(c,t,teg1);
return C_UDSI_G(c,t,teg1)[0];
}

I don't have any errors in this UDSs but, is it correct as per the given equation? Please let me know.
And also there is a term 'J' in the equation for which I need to create a profile on which I am still working.

[sahoo]

And what can you say about the following error:-
..\..\src\teg2.c(12): error C2065: 'thread': undeclared identifier
..\..\src\teg2.c(12): error C2223: left of '->t' must point to struct/union

I get this error frequently. I don't get this, since thread is a data type why do we need to declare it?
I get this error for the following code :-

#include "udf.h"
#include "math.h"

enum
{
teg2,
N_REQUIRED_UDS
};

DEFINE_EXECUTE_AT_END(execute_at_end)
{
Thread *t = thread->t;
cell_t c = F_C(c,thread);
real T = C_T(c,t);
begin_c_loop(c,t)
{
C_UDSI(c,t,teg2) = 8.439e-4 - 3.81e-6*T + 6.736e-9*pow(T,-9.) - 3.934e-12*pow(T,-12.);
}
end_c_loop(c,t)
}

I have tried to solve following many posts, but still I get it in every code.

[CeesH]

what are you trying to do with the thread t thing? point to itself?

I think you are looking for

Thread *t;
begin_thread_loop_c
{ - insert the cell loop -}

With that, you'll loop over all threads (and then all cells within them)

If you want to select a single thread, use:

t = Lookup_Thread(domain,zone_ID);

with the zone_ID being the cell zone or boundary zone number in FLUENT.

[sahoo]

yeah I got it. You mean I don't need to point to itself if I am going to use it in the UDS to store another value.

Thank you