3D velocity profile UDF

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 November 16, 2012, 18:31 3D velocity profile UDF #1 New Member   Hadi Join Date: Nov 2012 Location: Netherlands Posts: 2 Rep Power: 0 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) }

November 17, 2012, 05:46
#2
Senior Member

Daniele
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Location: Italy
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Quote:
 Originally Posted by hadiCFD 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"

{
face_t f;
real x[ND_ND];

{
F_CENTROID(x,f,t);
}
}```
Verify the position of your geometry; as an example I centered a parallelepiped in 0,0,0.
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Last edited by ghost82; November 17, 2012 at 06:40.

 November 18, 2012, 08:23 #3 New Member   Hadi Join Date: Nov 2012 Location: Netherlands Posts: 2 Rep Power: 0 Thank you ghost82 How can I verify the position of my geometry? I upload my geometry. Thank you

November 18, 2012, 10:03
#4
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Daniele
Join Date: Oct 2010
Location: Italy
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Quote:
 Originally Posted by hadiCFD 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
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 December 4, 2012, 02:32 #5 New Member   jianglei Join Date: May 2012 Location: xiamen Posts: 12 Rep Power: 5 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

December 4, 2012, 02:32
#6
New Member

jianglei
Join Date: May 2012
Location: xiamen
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Rep Power: 5
Quote:
 Originally Posted by ghost82 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 ?
Regards

December 5, 2012, 04:13
#7
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Daniele
Join Date: Oct 2010
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Quote:
 Originally Posted by dragonship2011 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.

December 5, 2012, 06:39
#8
New Member

jianglei
Join Date: May 2012
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Quote:
 Originally Posted by ghost82 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 .

December 5, 2012, 10:16
#9
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Daniele
Join Date: Oct 2010
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Quote:
 Originally Posted by dragonship2011 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..

December 5, 2012, 20:29
#10
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jianglei
Join Date: May 2012
Location: xiamen
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Quote:
 Originally Posted by ghost82 ok understand, but unfortunately I haven't an answer..
thank you all the same.

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