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-   -   3D velocity profile UDF (http://www.cfd-online.com/Forums/fluent-udf/109414-3d-velocity-profile-udf.html)

hadiCFD November 16, 2012 18:31

3D velocity profile UDF
 
Hi guys

I would like to define a 3D velocity profile but I don't know how. I read lots of 2D examples, but I am still confused about 3D. Is there any one who can help me?
It is one of the samples for 2D How can I add the third dimension to this code?

The desired velocity is
Vz = (1-(x^2+y^2)/25)

#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) = 20. - y*y/(.0745*.0745)*20.;
}
end_f_loop(f, thread)
}

ghost82 November 17, 2012 05:46

1 Attachment(s)
Quote:

Originally Posted by hadiCFD (Post 392629)
Hi guys

I would like to define a 3D velocity profile but I don't know how. I read lots of 2D examples, but I am still confused about 3D. Is there any one who can help me?
It is one of the samples for 2D How can I add the third dimension to this code?

The desired velocity is
Vz = (1-(x^2+y^2)/25)


I think this should work:

Code:

#include "udf.h"

DEFINE_PROFILE(my_velocity, thread, position)
{
  face_t f;
  real x[ND_ND];

  begin_f_loop(f, thread)
    {
    F_CENTROID(x,f,t);
    F_PROFILE(f, thread, position) = (1.-(x[0]*x[0]+x[1]*x[1])/25.);
    }
  end_f_loop(f, thread)
}

Verify the position of your geometry; as an example I centered a parallelepiped in 0,0,0.

hadiCFD November 18, 2012 08:23

Thank you ghost82
How can I verify the position of my geometry?

I upload my geometry. Thank you

http://s9.postimage.org/o9xptv5v3/Untitled1.jpg

ghost82 November 18, 2012 10:03

1 Attachment(s)
Quote:

Originally Posted by hadiCFD (Post 392775)
Thank you ghost82
How can I verify the position of my geometry?

I upload my geometry. Thank you

Imagine this simple example: a parallelepiped with its base centered in xy plane (figure on the left) and a parallelepiped not centered in the xy plane (figure on the right); imagine also that this base is the inlet velocity.

Your Vz velocity is a function of x and y coordinate, so each of the two cases will have different profiles, because x and y coordinates are different; according to this, you have to take into account the position of your inlet face in respect to the origin;

Eventually, you can translate your geometry in pre-processing, or alternatively you can modify your Vz formula, considering a translation transformation.

Daniele

dragonship2011 December 4, 2012 02:32

ghost82,
I have a question to ask for you .In a non-regulation shape, for example ,ships , how can I get the center of gravity and buoyant coordinates in the Fluent software ?
Please help me.
Regards

dragonship2011 December 4, 2012 02:32

Quote:

Originally Posted by ghost82 (Post 392790)
Imagine this simple example: a parallelepiped with its base centered in xy plane (figure on the left) and a parallelepiped not centered in the xy plane (figure on the right); imagine also that this base is the inlet velocity.

Your Vz velocity is a function of x and y coordinate, so each of the two cases will have different profiles, because x and y coordinates are different; according to this, you have to take into account the position of your inlet face in respect to the origin;

Eventually, you can translate your geometry in pre-processing, or alternatively you can modify your Vz formula, considering a translation transformation.

Daniele

ghost82,
I have a question to ask for you .In a non-regulation shape, for example ,ships , how can I get the center of gravity and buoyant coordinates in the Fluent software ?
Please help me.
Regards

ghost82 December 5, 2012 04:13

Quote:

Originally Posted by dragonship2011 (Post 395606)
ghost82,
I have a question to ask for you .In a non-regulation shape, for example ,ships , how can I get the center of gravity and buoyant coordinates in the Fluent software ?
Please help me.
Regards

Hi,
specify in details your problem, you may better open a new thread.

dragonship2011 December 5, 2012 06:39

Quote:

Originally Posted by ghost82 (Post 395856)
Hi,
specify in details your problem, you may better open a new thread.

hi,thank you very much for reply. You know , A ship is running in the water,it is carried by buoyant .In the software of Fluent ,how can I get the center coordinate of buoyant .

ghost82 December 5, 2012 10:16

Quote:

Originally Posted by dragonship2011 (Post 395885)
hi,thank you very much for reply. You know , A ship is running in the water,it is carried by buoyant .In the software of Fluent ,how can I get the center coordinate of buoyant .

ok understand, but unfortunately I haven't an answer..

dragonship2011 December 5, 2012 20:29

Quote:

Originally Posted by ghost82 (Post 395936)
ok understand, but unfortunately I haven't an answer..

thank you all the same.


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