[molixu]

Hi!
There is error as followed when I try to add the UDF boundary condition:
Error:
FLUENT received fatal signal (ACCESS_VIOLATION)
1. Note exact events leading to error.
2. Save case/data under new name.
3. Exit program and restart to continue.
4. Report error to your distributor.
Error Object: ()
I can't figure out what's the problem. I want to calculate the total heat added to the model by the function:
Q=cp*density*volume*(tempn-templ);
Q_tot +=Q;

Here's my UDF code, plz help me with that.. Thank you!!

#include "udf.h"
real Q_tot=0;
DEFINE_PROFILE (unsteady_heatflux, thread, position)
{
Domain *d;
real cp=880;
real density=2180;
real tempn, templ, volume, Q;
Thread *t;
cell_t c;
d= Get_Domain(2); /*Get the domain using Fluent utility *//*Loop over all cell threads in the domain*/
thread_loop_c(t,d) /*Compute Q */ /*Loop over all cells */
begin_c_loop(c,t)
{
real time= RP_Get_Real("flow-time");
real b=(int)(time/3600)+1;
int i=(int)((b-1)/24);
real Heat[4]={278.5, 280.7, 278.5, 280.5};
volume=C_VOLUME(c,t); /* get cell volume */
templ=C_T_M1(c,t); ; /*Get cell tempertuare of previous step*/
tempn=C_T(c,t); /*Get cell tempertuare*/
Q=cp*density*volume*(tempn-templ);
Q_tot +=Q;
if (Q_tot<= Heat[i])
F_PROFILE(c,t,position)=60;
else F_PROFILE(c,t,position)=0;
}
end_c_loop(c,t)
}

[dmoroian]

...
d= Get_Domain(2);
...

Are you computing a multiphase model? If not, then this is an error, and 2 should be replaced with 1:

...
d= Get_Domain(1);
...

In any case it is a good practice to check for NULL pointer:

...
if(NULL == (d= Get_Domain(1)))
   Error("NULL pointer assignment!\n");
...

[molixu]

Thank you for your reply.
I've noticed that and changed to d= Get_Domain(1);but it still doesn't work. I can't even initialize...the same error..

Originally Posted by dmoroian

...
d= Get_Domain(2);
...

Are you computing a multiphase model? If not, then this is an error, and 2 should be replaced with 1:

...
d= Get_Domain(1);
...

In any case it is a good practice to check for NULL pointer:

...
if(NULL == (d= Get_Domain(1)))
   Error("NULL pointer assignment!\n");
...

[dmoroian]

Ok, now I see few mistakes more:
1. You don't need the domain pointer since you already have the face thread "thread" given by the solver.
2. You're looping over the cell threads but what you need is a face thread, and when you mix them, you get an error (F_PROFILE(c,t,position) will give you a segmentation violation if you don't use a face thread).

So, remove

d= Get_Domain(2); /*Get the domain using Fluent utility *//*Loop over all cell threads in the domain*/
thread_loop_c(t,d) /*Compute Q */ /*Loop over all cells */
begin_c_loop(c,t)

and replace it with:

begin_f_loop(f,thread)
...
F_PROFILE(f,thread,position) = ...
...

You will still need the cell id and cell thread. Check section 2.3.26.4 in the fluent 13 udf manual to see how is done.

[molixu]

domoroian,
I've changed my codes as follows. My case is a simple one about heat transfer in solid,2D model. What I want to realize is: get the temperature of recent step and previous step of all the cells in the X-Y face, using them to calculate the heat obtained of the domain,(Q=c*m*delt(T) )and accumulate the value of Q for each day (real time in interation). Once the Q reach a certain value, the BC of imposed temperature 333K was changed to equaling the temp of the adjacent cell temperature. How can I store the value Q after each interation? is my codes correct?
And there'are some errors when compiling.
1.udf_names.c(7) : error C2059: syntax error : “}”
2.udf_names.c(8) : warning C4034: sizeof return 0

#include "udf.h"

#define cp 800
#define density 2180
DEFINE_PROFILE (unsteady_temp,t,index)
{
float tempn,templ,volume,Q,Q_tot,time,a,b,tempad;
int i;
float Heat[5]={278.5, 280.7, 278.5, 280.5, 285.2};
Domain *d;
Thread *ct,*t0;
cell_t c,c0;
face_t f;
time = RP_Get_Real("flow-time");
a =time/3600;
b =a/24;
d = Get_Domain(1);
i=(int)(((int)a)/24);
if (b==(int)b)  
Q_tot=0;
thread_loop_c(ct,d)  /*Compute Q */ /*Loop over all threads in the domain */
{
begin_c_loop(c,ct) /*Loop over all cells */
   {
volume=C_VOLUME(c,ct); /* get cell volume */
templ=C_T_M1(c,ct); /*Get cell tempertuare of previous step*/
tempn=C_T(c,ct);   /*Get cell tempertuare*/
Q=cp*density*volume*(tempn-templ);
Q_tot +=Q;
   }
 end_c_loop(c,ct)
}
if (Q_tot<= Heat[i])
begin_f_loop(f,t)
{   
F_PROFILE(f,t,index)=333;  /*BC:Temp=333K*/
}
end_f_loop(f,t) 
else
begin_f_loop(f,t)
{   
c0 = F_C0(f,t);
t0 = THREAD_T0(t);
tempad=C_T(c0,t0); /*temperature of adjacent cell*/
F_PROFILE(f,t,index)=tempad; 
}
end_f_loop(f,t)
}

Could you give me some advise? Many thanks!

Originally Posted by dmoroian

Ok, now I see few mistakes more:
1. You don't need the domain pointer since you already have the face thread "thread" given by the solver.
2. You're looping over the cell threads but what you need is a face thread, and when you mix them, you get an error (F_PROFILE(c,t,position) will give you a segmentation violation if you don't use a face thread).

So, remove

d= Get_Domain(2); /*Get the domain using Fluent utility *//*Loop over all cell threads in the domain*/
thread_loop_c(t,d) /*Compute Q */ /*Loop over all cells */
begin_c_loop(c,t)

and replace it with:

begin_f_loop(f,thread)
...
F_PROFILE(f,thread,position) = ...
...

You will still need the cell id and cell thread. Check section 2.3.26.4 in the fluent 13 udf manual to see how is done.

[ComputerGuy]

Molixu,

Please see the reply here: http://www.cfd-online.com/Forums/flu...tion-rate.html


Please stop posting the same question to several threads.