these codes are written in C or C++, i need a udf code for a flow
which enters a block from an injection that is the velocity is zero
when time is zero, then the flow is reaches a constant value (say 1
m/s) and then again the velocity is zero at t=a seconds.

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Clarification of Question by woo_rawolf-ga on 08 Feb 2005 15:30 PST

these codes are written in C or C++, i need a udf code for a flow
which enters a block from an injection that is the velocity is zero
when time is zero, then the flow is reaches a constant value (say 1
m/s) and then again the velocity is zero at t=a seconds.
Imagine the is supposed to enter into the skin from an injection, how
will the velocity change according to time.

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Request for Question Clarification by maniac-ga on 08 Feb 2005 19:02 PST

Hello Woo_rawolf,

You may get an answer more quickly if you define the term
  UDF
as well as describe the problem you are trying to solve a little more
clearly. For example, I found a reference to Computational Fluid
Dynamics where "UDF" stood for "User Defined Function". This
definition may indeed be what you are looking for but the application
(injecting medicine into skin?) does not seem to fit.

  --Maniac

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Clarification of Question by woo_rawolf-ga on 08 Feb 2005 22:09 PST

I am workin on a software called Fluent, and im working on a diffusion
problem(to see blood/medicine)seepage from a particular tissue for
which I need to set a user defined function (UDF). usually this
function is written in C/C++ using sum compiler, which will be a
velocity profile i have this UDF here for a parabolic velocity
profile, for example

/***********************************************************************/
/* vprofile.c
*/
/* UDF for specifying steady-state velocity profile boundary condition
*/
/***********************************************************************/
#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) = 8.*y - 8.*y*y;
    }
  end_f_loop(f, thread)
}

what happens with this as a UDF is that the flow will enter as a
steady state parabola. Appreciate your reply. waitin for more.thanks

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Request for Question Clarification by maniac-ga on 09 Feb 2005 19:04 PST

Hello Woo_rawolf,

Much better, thanks. I guess you ARE doing CFD's.

Unfortunately, I am not familiar with Fluent (http://www.fluent.com/)
but I have an inquiry to their customer support group to see if I can
get access to the appropriate documentation to answer your question.
It is also possible that another researcher may be able to provide a
complete answer as well.

  --Maniac