I am trying to use UDM for the first time. I have written the part of the code shown below, where eta(f) is a function in another part of the code. I would have assumed the same value that is printed for over_pot in the printf line would be the value that appeared in my xy plots in fluent. When I make the xy plot I only get a value of 0.00000. Any reason why this is occuring?

DEFINE_PROFILE(tile_conc_spec, thread_sol, i)

{

face_t f;

begin_f_loop(f, thread_sol)

{

real over_pot = eta(f);

F_UDMI(f, thread_sol, 0) = over_pot;

printf ("\nover_pot = %g, at face %d", over_pot, f);

F_PROFILE(f, thread_sol, i) = c_bulk*concvar(f)/(concvar(f)+1);

} end_f_loop(f, thread_sol)

}

You're saving your values only on the boundary where you define your profile, so you should be able to plot it only there, by selecting the boundary in the XY-plot panel.

Hi

ap

The thread that I am defining the profile on "thread_sol" is the same one that I am applying the UDM to, it is also the one I am trying to XY plot in fluent. I still get 0.000 for all face values on that face thread. Is it because all the values are negative?

I don't think this has to do with the sign of values.

Hi

ap

[balki]

Hi Andrew, I hope you would have solved this problem. I'm also facing the same problem can you please let me know the solution?

Thanks
krishnan

[Kanarya]

Originally Posted by balki

Hi Andrew, I hope you would have solved this problem. I'm also facing the same problem can you please let me know the solution?

Thanks
krishnan

Hi I have the same problem. the values are 0.did u solve the problem my code is:
#include "udf.h"
DEFINE_PROFILE(outlet_mf,t,i)
{
face_t f;
real flow;
begin_f_loop(f,t)
{
flow+=F_FLUX(f,t);
F_UDMI(f,t,0)=flow;
}
end_f_loop(f,th);

}

thanks in advance!!!

[balki]

Hi Kanarya, I had the same problem. When I used C_UDMI instead of F_UDMI, it worked as expected. I dont know why.

[Kanarya]

Originally Posted by balki

Hi Kanarya, I had the same problem. When I used C_UDMI instead of F_UDMI, it worked as expected. I dont know why.

Hi,
Thanks for the answer!
did you use the function F_FLUX(f,t)? how is it possible to read face and to save in cell?

thanks again...

[balki]

Originally Posted by Kanarya

Hi,
Thanks for the answer!
did you use the function F_FLUX(f,t)? how is it possible to read face and to save in cell?

thanks again...

Hi, I didn't use F_FLUX.

how is it possible to read face and to save in cell? I have the same doubt, anyhow as I said earlier, C_UDMI solved the problem. If you find the answer, please let me know....

Balki

[Kanarya]

Hi,

which function is suitable to save mass flow at outlet..do you think, is define_execute_at_end OK for it?

thanks for advance..!

[Kanarya]

Originally Posted by balki

Hi, I didn't use F_FLUX.

how is it possible to read face and to save in cell? I have the same doubt, anyhow as I said earlier, C_UDMI solved the problem. If you find the answer, please let me know....

Balki

Hi Balki,
#include "udf.h"
DEFINE_EXECUTE_AT_END(measure_mass_flow)
{
real mass_flow;
real mass_flow_g;
Domain *d=Get_Domain(1);
cell_t c;
face_t f;
Thread *mixture_thread = Lookup_Thread(d,4);
Thread **pt = THREAD_SUB_THREADS(mixture_thread);
Thread *tp = pt[0];
Thread *ts = pt[1];

mass_flow=0.;
//mass_flow=0.;
mp_thread_loop_f(mixture_thread,d,pt)

if( THREAD_ID(mixture_thread) == 4 )

{
begin_f_loop(f,mixture_thread)

{
mass_flow+=F_FLUX(f,ts);

if(N_UDM > 0 && BOUNDARY_FACE_THREAD_P(ts))

C_UDMI(f,ts,0)=mass_flow;
}
end_f_loop(f,mixture_thread)
}


Message("mass_flow:%g/n",mass_flow);

}

I am trying to save mass flow at outlet. but it gives always zero, could you give me a hint? thanks a lot in advance!!!

[FarzinD]

Originally Posted by balki

Hi Kanarya, I had the same problem. When I used C_UDMI instead of F_UDMI, it worked as expected. I dont know why.

I also came up with this problem. I think its just not enough to have only Face User-Defined memory of a cell to make plots. Considering that Fluent calculates and stores variables on cell Centers, it is needed to store the value of both Cell and it's Face within a single User-Defined Memory Location.

[sewgolam]

Can you please explain how to make a C_UDMI in fluent.
i tryed to read the manual but still no clue what im doing. I want to store reaction product and give it back as mass source.

please help