[Ratel]

Hi,

I have written a UDF that specifies an atmospheric boundary layer (ABL) velocity profile at the inlet of a two-dimensional domain.

My ABL equation is valid for a domain where the origin lies on the bottom wall. For my work the domain is going to be translated downwards (So that the bottom wall will be in the negative y region)- this will happen automatically during design point runs in workbench and my UDF has to compensate for this by also translating the profile.

The attached UDF therefore loops through the boundary faces and nodes to find the most negative point (The bottom wall) and uses this value to translate the profile by the same amount. Below is my UDF:

--------------------------------------------------------------------
#include "udf.h"

#define uABL 0.2674; /* Atmospheric BL friction velocity */
#define k 0.41; /* Von Karman constant */
#define y0 4.6875E-4;; /* Aerodynamic roughness length */

/* Stream-wise velocity profile */
DEFINE_PROFILE(x_velocity,thread,nv)
{
real pos[ND_ND], y, yCnew, yNnew, yCold, yNold; /* variable declarations */
yCold = 1000; /* Initial values to ensure the two if-loops are entered */
yNold = 1000;

int n;
face_t f; /* f is a face thread index */
Node *node;

begin_f_loop(f, thread) /* loop through all the faces of the boundary*/
{
F_CENTROID(pos, f, thread); /* determine the centroid coordinate of the current face*/
yCnew = pos[1];

if (yCnew < yCold) /* if the current centroid coordinate is smaller than the previous one, loop through the nodes of that face*/
{
f_node_loop(f, thread, n)
{
node = F_NODE(f,thread,n);
yNnew = NODE_Y(node); /* nodal coordinate */

if (yNnew < yNold) /*if the current nodal coordinate is smaller than the previous one, replace it*/
{yNold = yNnew;}
}
yCold = yCnew; /* replace the previous centroid coordinate */
}
}
end_f_loop(f, thread)

begin_f_loop(f, thread) /*loop through the faces agian and specify te velocity profile */
{
F_CENTROID(pos, f, thread);
y = pos[1];
F_PROFILE(f, thread, nv) = uABL / k*log((y - yNold) / y0); /* translated velocity profile */
}
end_f_loop(f,thread)
}
--------------------------------------------------------------------------

When trying to compile it, I get the following message in Fluent:

---------------------------------------------------------------------
Copied C:\Dawie\Meesters\CFD Werk\UDF_Compile_Toets\UDF_Compile-Toets_files\dp0\FLU-2\Fluent\VelProf_Translated.c to libudf\src
udf_names.c and user_nt.udf files in 2ddp_host are upto date.
(system "copy "C:\PROGRA~1\ANSYSI~1\v150\fluent"\fluent15.0.0\sr c\makefile_nt.udf "libudf\win64\2ddp_host\makefile" ")
1 file(s) copied.
(chdir "libudf")(chdir "win64\2ddp_host")# Generating ud_io1.h
VelProf_Translated.c
..\..\src\VelProf_Translated.c(42) : error C2143: syntax error : missing ';' before '/'
..\..\src\VelProf_Translated.c(42) : error C2143: syntax error : missing ')' before ';'
..\..\src\VelProf_Translated.c(42) : error C2100: illegal indirection
..\..\src\VelProf_Translated.c(42) : error C2059: syntax error : ')'
udf_names.c and user_nt.udf files in 2ddp_node are upto date.
(system "copy "C:\PROGRA~1\ANSYSI~1\v150\fluent"\fluent15.0.0\sr c\makefile_nt.udf "libudf\win64\2ddp_node\makefile" ")
1 file(s) copied.
(chdir "libudf")(chdir "win64\2ddp_node")# Generating ud_io1.h
VelProf_Translated.c
..\..\src\VelProf_Translated.c(42) : error C2143: syntax error : missing ';' before '/'
..\..\src\VelProf_Translated.c(42) : error C2143: syntax error : missing ')' before ';'
..\..\src\VelProf_Translated.c(42) : error C2100: illegal indirection
..\..\src\VelProf_Translated.c(42) : error C2059: syntax error : ')'

Done.
-------------------------------------------------------------------------

I would appreciate it if anyone can help me with the syntax error that I am getting!

Thanks!

[Ratel]

Line 42 is the line where the profile is being defined:
F_PROFILE(f, thread, nv) = uABL / k*log((y - yNold) / y0); /* translated velocity profile */

[pakk]

The problem is in your #defines:

#define uABL 0.2674; /* Atmospheric BL friction velocity */
#define k 0.41;	 /* Von Karman constant */
#define y0 4.6875E-4;; /* Aerodynamic roughness length */

Remove the semicolons there:

#define uABL 0.2674 /* Atmospheric BL friction velocity */
#define k 0.41	 /* Von Karman constant */
#define y0 4.6875E-4 /* Aerodynamic roughness length */

[Ratel]

Thank you very much pakk, your advice solved my problem!

Kind Regards

[jyothsna k]

Thank you very much