URGENT!!! F_UDSI at symmetry boundary

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March 4, 2010, 16:41
URGENT!!! F_UDSI at symmetry boundary
#1
Member

Join Date: Mar 2009
Location: Istanbul, Turkiye
Posts: 45
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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_loop_f(tf, domain)/* loops over all face threads in a domain*/
{
begin_f_loop(f, tf)    /* loops over faces in a face thread  */
{
{
Message("face id = %d, UDS0 value = %12.5e",f, F_UDSI(f, tf, 0));
}
}
}```
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]

Last edited by gemini; March 5, 2010 at 03:34.

March 8, 2010, 05:51
#2
Senior Member

Ji Junjie
Join Date: Feb 2010
Location: Shanghai, China
Posts: 109
Rep Power: 8
Quote:
 Originally Posted by gemini 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;
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 */
{
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);
}
}

}
}

March 10, 2010, 04:20
#3
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Join Date: Mar 2009
Location: Istanbul, Turkiye
Posts: 45
Rep Power: 9
Quote:
 Originally Posted by gearboy 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; Thread *tf,*t0; Domain*domain=Get_Domain(1); real NV_VEC(dist_vector); real f_centoid[ND_ND],c_centroid[ND_ND]; real face_value,cell_value; thread_loop_f(tf, domain)/* loops over all face threads in a domain*/ { if (THREAD_F_AXIS==THREAD_TYPE(tf)) /* if the thread is an axis thread*/ { 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); t0=THREAD_T0(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); } end_f_loop(f, f_thread) } } }
Hi,

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

Also, THREAD_F_AXIS didn't worked for SYMMETRY bc's. Instead "THREAD_F_SYMMETRIC" works well...

Thanks.

Last edited by gemini; March 10, 2010 at 05:00.

March 10, 2010, 22:50
#4
Senior Member

Ji Junjie
Join Date: Feb 2010
Location: Shanghai, China
Posts: 109
Rep Power: 8
Quote:
 Originally Posted by gemini 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.

March 11, 2010, 02:23
#5
Member

Join Date: Mar 2009
Location: Istanbul, Turkiye
Posts: 45
Rep Power: 9
Quote:
 Originally Posted by gearboy 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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