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UDF's are User Defined Functions

They are typically written in C, but can be written in Fortran. Fluent has a C interpreter built in, so you don't need one unless aspects of the calculation (specific Fluent calls, speed of calculation, etc) require compilation.

To impose a fully developed profile at a wall, you must loop over all faces of the wall and set the velocity magnitude (or, perhaps, a vector component) equal to the velocity you obtain from fully developed flow.

In the code below, I assume the following:
1) Fully developed laminar flow
2) 2-D flow in the x-direction
3) An inlet face which extends from 0.5 to -0.5 in the y-direction
4) A maximum centerline velocity of 10

Code:

#include "udf.h"



DEFINE_PROFILE(inlet_x_velocity, thread, position) 

{

  real x[ND_ND];                /* this will hold the position vector */

  real y;

  face_t f;



  begin_f_loop(f, thread)

    {

      F_CENTROID(x,f,thread);

      y = x[1];

      F_PROFILE(f, thread, position) = 10.-10.*(y*y/(0.5*0.5));

    }

  end_f_loop(f, thread)

}

I haven't tested it, but it should function OK with few, if any, changes. I don't know which direction you've specified as vertical, so you'll need to adapt a few things in the code above to fit your application.

Go here: http://combust.hit.edu.cn:8080/fluen.../udf/node2.htm
for more information on UDFs.

ComputerGuy