[Tushar_Telmasre]

I am trying to learn the use of UDMs.
I read through ansys help and tried to execute define on demand udm.

the code is
/************************************************** ********************
UDF to calculate temperature field function and store in
user-defined memory. Also print min, max, avg temperatures.
************************************************** *********************/
#include "udf.h"

DEFINE_ON_DEMAND(on_demand_calc)
{
Domain *d; /* declare domain pointer since it is not passed as an
argument to the DEFINE macro */
real tavg = 0.;
real tmax = 0.;
real tmin = 0.;
real temp,volume,vol_tot;
Thread *t;
cell_t c;
d = Get_Domain(1); /* Get the domain using ANSYS Fluent utility */

/* Loop over all cell threads in the domain */
thread_loop_c(t,d)
{

/* Compute max, min, volume-averaged temperature */

/* Loop over all cells */
begin_c_loop(c,t)
{
volume = C_VOLUME(c,t); /* get cell volume */
temp = C_T(c,t); /* get cell temperature */

if (temp < tmin || tmin == 0.) tmin = temp;
if (temp > tmax || tmax == 0.) tmax = temp;

vol_tot += volume;
tavg += temp*volume;

}
end_c_loop(c,t)

tavg /= vol_tot;

printf("\n Tmin = %g Tmax = %g Tavg = %g\n",tmin,tmax,tavg);

/* Compute temperature function and store in user-defined memory*/
/*(location index 0) */

begin_c_loop(c,t)
{
temp = C_T(c,t);
C_UDMI(c,t,0) = (temp-tmin)/(tmax-tmin);
}
end_c_loop(c,t)

}
}


This is the same as given in the ansys help.

further i defined a memory location in fluent.

solved the following problem.
A Square aluminium block of lenght 1mm. properties as given in fluent.
left boundry: 600K temperature.
Right boundry: 100K temperature.
solved the problem with time step of 1e-5 for 100 time steps.

now when i am trying to execute on demand the function it is giving me a
segmentation fault. what is wrong here.

As far as i know segmentation fault occurs when code tries to access undefined memory location. I defined 1 user defined memory slot. still it is not working.
what needs to be done.
Please help.

[pakk]

You are correct that this error indicates that you are trying to access a memory location that does not exist. The next step is to identiy where in your code this happens.

It could be in three places: C_UDMI(c,t,0), C_VOLUME(c,t), C_T(c,t)

If you remove the line with C_UDMI(c,t,0), do you still get this error?
If you replace C_VOLUME(c,t) by 0.1, do you still get this error?
If you replace C_T(c,t) by 300, do you still get this error?

If the error disappears, you know which line causes the error. And then think about why it could be. If C_T is the problem, are you sure that all cells have a temperature associated?