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-   -   URGENT!!! F_UDSI at symmetry boundary (http://www.cfd-online.com/Forums/fluent-udf/73334-urgent-f_udsi-symmetry-boundary.html)

 gemini March 4, 2010 16:41

URGENT!!! F_UDSI at symmetry boundary

Hi,

In FLUENT udf manual following statement is given,

Quote:
 Note that F_UDSI is available for wall and flow boundary faces, only. If a UDS attempts to access any other face zone, then an error will result.

Then, I tried to test this in a simple 3D uds diffusion problem where the domain has symmetry boundary condition. After convergence, I applied following function to printout the face values of uds at all boundaries:

Code:

```face_t f; Thread *tf; thread_loop_f(tf, domain)/* loops over all face threads in a domain*/   {   begin_f_loop(f, tf)    /* loops over faces in a face thread  */   {     if (BOUNDARY_FACE_THREAD_P(tf))       {           Message("face id = %d, UDS0 value = %12.5e",f, F_UDSI(f, tf, 0));        }   }                          end_f_loop(f, f_thread) }```
However, execution of this script resulted in an error. So, is there any way to prevent the use of F_UDSI at symmetry bc's? or How can I extract the type of bc of a particular boundary face?

thanks

[/COLOR]

 gearboy March 8, 2010 05:51

Quote:
 Originally Posted by gemini (Post 248619) Hi, In FLUENT udf manual following statement is given, Then, I tried to test this in a simple 3D uds diffusion problem where the domain has symmetry boundary condition. After convergence, I applied following function to printout the face values of uds at all boundaries: Code: `face_t f;` Code: ```Thread *tf; thread_loop_f(tf, domain)/* loops over all face threads in a domain*/ {   begin_f_loop(f, tf)    /* loops over faces in a face thread  */   {     if (BOUNDARY_FACE_THREAD_P(tf))       {           Message("face id = %d, UDS0 value = %12.5e",f, F_UDSI(f, tf, 0));        }   }                          end_f_loop(f, f_thread) }``` However, execution of this script resulted in an error. So, is there any way to prevent the use of F_UDSI at symmetry bc's? or How can I extract the type of bc of a particular boundary face? thanks [/COLOR]
It seems that there are no values stored on the non-wall boundary. This has been also an question confusing me. Maybe it's a bug of Fluent. If it is urgent for you , you can use the following better-than-nothing solution. It uses the neighbour cell's uds value , uds gradient, and distance vector to calculate the face value.

#include "udf.h"
DEFINE_ON_DEMAND(test)
{
face_t f;
cell_t c0;
Domain*domain=Get_Domain(1);
real NV_VEC(dist_vector);
real f_centoid[ND_ND],c_centroid[ND_ND];
real face_value,cell_value;
{
{
begin_f_loop(f, tf) /* loops over faces in a face thread */
{
F_CENTROID(f_centoid,f,tf); //centroid of a face
c0=F_C0(f,tf);
C_CENTROID(c_centroid,c0,t0); //centroid of the neighbour cell
NV_DD(dist_vector,=,f_centoid[0],f_centoid[1],0,-,c_centroid[0],c_centroid[1],0);
face_value=C_UDSI(c0,t0,0)+NV_DOT(C_UDSI_G(c0,t0,0 ),dist_vector);
cell_value=C_UDSI(c0,t0,0);
Message0("x coord.=%g,face value=%g,cell value=%g\n",f_centoid[0],face_value,cell_value);
}
}

}
}

 gemini March 10, 2010 04:20

Quote:
Hi,

Can your script be used for calculation of face value at the interior faces by just removing the following line?

Thanks.

 gearboy March 10, 2010 22:50

Quote:
 Originally Posted by gemini (Post 249281) Hi, Can your script be used for calculation of face value at the interior faces by just removing the following line? if (THREAD_F_AXIS==THREAD_TYPE(tf)) /* if the thread is an axis thread*/ Also, THREAD_F_AXIS didn't worked for SYMMETRY bc's. Instead "THREAD_F_SYMMETRIC" works well... Thanks.
The script can be used for interior faces if the F_T macro doesn't work. And I misunderstood the case as an axial symmetric one. Sorry.

 gemini March 11, 2010 02:23

Quote:
 Originally Posted by gearboy (Post 249466) The script can be used for interior faces if the F_T macro doesn't work. And I misunderstood the case as an axial symmetric one. Sorry.
Hi,

Your script was very useful, and as you said, it can be used for calculating face fluxes of UDS and then they can be used anywhere in your model.

thanks again.

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