Parabolic Profile of velocity
How can I introduce a parabolic profile of velocity at the entrance of a straight tube?

Greetings Roberto,
Since you're question is so generic, here's a generic answer: http://www.google.com/imghp?q=parabolic+profile ;) But seriously, what's the context? Is it:
Bruno PPS: I've moved this thread to the subforum dedicated to FLUENT, given the response on the next post ;) 
Bruno, you've got a good sense of humor ;). Besides that I'm talking about Fluent 14.0. I need a boundary condition that allows me to introduce a completely developped parabolic profile of velocity of a fluid entering a straight tube (3D). I can either create a very long tube, or create this profile in some way, but I don't know how.

Hi, I am working in similar 3D case. At the moment, my macro is this:
____________________________________ #include "udf.h" #define S 0.0016 DEFINE_PROFILE(inlet_x_velocity, thread, index) { real x [ND,ND]; real y; real z; face_t,f; begin_f_loop(f,thread) { F_CENTROID(x,f,thread) y=x[1] z=x[2] if (y>=S) F_PROFILE(f,thread,index)=0.55*double log (double (y/0.0016)) } end_f_loop(f,thread) } _________________________________ But on compiling my UDF I get the error. Any ideas will be appreciated Thanks! 
Quote:

I'm trying with this one but it tells me Divergence detected in AMG solver :confused:
#include "udf.h" #define YMIN 1.2 #define YMAX 1.55 #define UMEAN 0.04150349 #define B 1./7. #define DELOVRH 0.5 DEFINE_PROFILE(x_velocity,t,i) { real y, del, h, x[ND_ND], ufree; /* variable declarations */ face_t f; h = YMAX  YMIN; del = DELOVRH*h; ufree = UMEAN*(B+1.); begin_f_loop(f,t) { F_CENTROID(x,f,t); y = x[1]; if (y <= del) F_PROFILE(f,t,i) = ufree*pow(y/del,B); else F_PROFILE(f,t,i) = ufree*pow((hy)/del,B); } end_f_loop(f,t) } 
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