3D model velocity profile
 

Hi!

I am simulating the air flow over desert surface. I need to define a parabolic function of the wind in the inlet domain. My model is 3D. The function I have to define is: u (z) = u * / k ln (z / zo), where u = average wind speed (m / s), u * = friction velocity (m / s); k = von Karman constant = 0.4, z = height above the surface (m) = zo = 0.00008 surface roughness.

I want to define a maximum speed in function, for example, 6 m/s.
http://subir.cc/thumbs/untitleoe.png

I need help with the UDF, I read the ANSYS FLUENT UDF Manual and exemples in this forum and I think that the macro is the following:

DEFINE_PROFILE(inlet_x_velocity, thread, position)
{
real x[ND_ND];
real y; // Vertical Distance
face_t f;
begin_f_loop(f, thread)
{
F_CENTROID(x,f,thread);
y = x[2];
F_PROFILE(f, thread, position) = (I need help here)

}

end_f_loop(f, thread)
}

Thanks for your help!:)