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Parabolic Profile of velocity

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Old   September 18, 2012, 07:49
Default Parabolic Profile of velocity
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Roberto
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How can I introduce a parabolic profile of velocity at the entrance of a straight tube?
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Old   September 18, 2012, 08:44
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Bruno Santos
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wyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nice
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:
  1. Purely in the mathematical sense?
  2. Purely in the mathematical sense, but in a CFD context/terminology?
  3. In a mathematical software, such as MATLAB or Mathematica?
  4. In a particular CFD software?
  5. In a CAD software?
  6. In a real life laboratory experiment?
Best regards,
Bruno

PPS: I've moved this thread to the sub-forum dedicated to FLUENT, given the response on the next post

Last edited by wyldckat; September 19, 2012 at 16:54. Reason: see "PPS"
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Old   September 19, 2012, 06:27
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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.
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Old   September 20, 2012, 07:02
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rayolau
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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!
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Old   September 20, 2012, 10:00
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Quote:
Originally Posted by Robbb View Post
I can either create a very long tube, or create this profile in some way, but I don't know how.
I would go for the long tube.
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Old   October 1, 2012, 07:03
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I'm trying with this one but it tells me Divergence detected in AMG solver


#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((h-y)/del,B);
}
end_f_loop(f,t)
}
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