obtaining wall distance for UDF
 

Hi all,

I need to calculate the distance from wall in my UDF. Apparently C_WALL_DIST(c,t) is no longer available and I cannot use it in my UDF.
Does anybody know any other solution? Or if fluent has replaced it with some other kind of Macro?

Thanks,
Ali

Moving post to the fluent forum. Please ensure you post on the right forum in future.

Hi,

which version of Fluent are you using ?
I am using C_WALL_DIST for v14.5 and v16, it works.
Write your UDF here if you want.

Fanch

Hi,

I am using Fluent v 16.2 and it does not work there.

Maybe you can try like this :
C_UDMI(c,t,0) = C_STORAGE_R(c,t,SV_WALL_DIST)

It is strange as in the headers file of v16.2, in the mem.h file, C_WALL_DIST is defined : #define C_WALL_DIST(c,t) C_STORAGE_R(c,t,SV_WALL_DIST)

Fanch

Do you use #include "mem.h" at the beginning of your UDF code ?

Fanch

Fanch,

Yes, I have included "mem.h" file.
I tried what you recommended but I received a segmentation error.
C_UDMI(c,t,0) = C_STORAGE_R(c,t,SV_WALL_DIST)

I have defined a UDM, so that would not be the problem.

Are you sure that C_WALL_DIST is defined in mem.h? How can I see the content of that? is there anyway that I can see the content of that header file?

Thanks,
Ali

If Fluent is installed on your local computer, you can go to this directory :
C:\Program Files\ANSYS Inc\v162\fluent\fluent16.2.0\src et you have all the headers file, with the definitions of all functions.

I only use C_WALL_DIST in DEFINE_ON_DEMAND macro. I don't understand why it is not working for you :/

I can show you my code if you want, maybe it comes from the loop you are using or something else

Fanch

Unfortunately I cannot access those files since I run fluent from a remote machine and I do not have admin privileges.
That would be great if you can do it. I can compare it with my own code and I will post my code in the next post for you to see.

thanks,
Ali

#include "udf.h"
#include "mem.h"
#include "math.h"
#include "dll.h" /* do not think it is useful in this case */
DEFINE_ON_DEMAND(y_plus)
{
#if RP_NODE
Domain *d;
Thread *t;
cell_t c;
face_t f;
d= Get_Domain(1);
if (! Data_Valid_P())
return;

thread_loop_c(t,d)
{
begin_c_loop(c,t)
{
C_UDMI(c,t,1) = C_WALL_DIST(c,t);
}
end_c_loop(c,t)
}
#endif
}

Fanch,

I receive segmentation error whenever I use C_WALL_DIST.
I even replicated the same code that you have posted here in another UDF and received the same error. I double-checked everything like UDMs and UDSs and everything seems to be fine.
It successfully is compiled but if I hook it to fluent, I will receive the error.
I will post my UDF here in the next post for you to see.

In this function I have to use wall distance macro to find F2 and this is where the segmentation error is produced.

real F2(cell_t c, Thread *t){

real c1,c2,d1;

c1=2*sqrt(C_UDSI(c,t,k))/(betastar*C_UDSI(c,t,w)*C_WALL_DIST(c,t));
c2=500*C_MU_L(c,t)/C_R(c,t)/(pow(C_WALL_DIST(c,t),2)*C_UDSI(c,t,w));

d1= MAX(c1,c2);
return tanh(d1*d1);
}

If I replace the C_WALL_DIST(c,t) with some constant value the error will go away.

Fanch,

did you try my code?

I asked a UDF specialist and he said this macro (C_WALL_DIST) is still available and it just has to be filled first.
Unfortunately I cannot ask him anymore.
Does anybody know what does that mean?