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-   -   [GAMBIT] How to set up a wind tunnel with interior? (https://www.cfd-online.com/Forums/ansys-meshing/63408-how-set-up-wind-tunnel-interior.html)

Zweeper April 7, 2009 15:10

How to set up a wind tunnel with interior?
 
1 Attachment(s)
Hello!

I have some huge problems with the following task: (see attachment)

I have to set up a wind tunnel (face 2), a smaller quader which has to act as interior for a smaller meshing setp (face 4) and an aerofoil in the middle.

My first problem is the substraction of the three faces.
Which steps i have to follow?

1. substract face 1 from face 4 (without retain or something?) gives then Face A
2. substract the new face A from face 2 (also without retain or something?

i think i have to set up face 4 as interior, right? do i have to do this after the substracting?


kind regards!

-mAx- April 8, 2009 00:42

-Substract face 4 with face 1, it generates face A
-Split face 2 with face A
You don't need to set any face as Interior

Zweeper April 8, 2009 03:43

okay, i did it your way, but now gambit meshes the area between face 4 and face 2, and the aerofoil in the middle (face 1). the area between face 1 and face 4 remains empty.

-mAx- April 8, 2009 03:50

hmm funny...
if you substract face4 with face1, what is the result?

Zweeper April 8, 2009 04:11

then it works. but when i split the faces afterwards, i have the porblem i wrote in the post before.

now i can mesh every face how it should be, but when i export this file and import it into fluent, face 4 has a behaviour of a normal wall. do i have to change the boundary coniditons into fluent or gambit of face 4?

(i know how to set up the other boundary conditions like velocity inlet, walls and pressure outlet)

Zweeper April 8, 2009 04:15

okay wait, now the mesh from face 2 is under the mesh from face 4 and face 1

-mAx- April 8, 2009 04:33

ok I assume the face 4 and face 1 are right substracted (I call this face A).
Try to split face 4 with the outer edges from A (rectangle)
Normally you shoul have 2 faces on the same location (face A and the face resulting from the split)
Delete the face resulting from the split.
All the edges should be right connected, but you can go and connect all edges (as security)

Zweeper April 8, 2009 04:54

okay, you mean i should use the "split face" option, select face 4 by "face", select "edges (virtual)" by "split with" and then i select the 4 edges from face 4, right?

when i do this, gambit shows the following error meessage:

face.4 could not be split with edge... which is coincident with the face boundary. Such a split may result in a degenerate geometry.



sorry, i know the "basics" form gambit, but for this project i have to to it with the inner face 4 and i have so huge problems with this assignment as you can see :(

-mAx- April 8, 2009 05:33

Quote:

Originally Posted by Zweeper (Post 212304)
okay, you mean i should use the "split face" option, select face 4 by "face", select "edges (virtual)" by "split with" and then i select the 4 edges from face 4, right?

when i do this, gambit shows the following error meessage:

face.4 could not be split with edge... which is coincident with the face boundary. Such a split may result in a degenerate geometry.

wait... you must split face 2 with the 4 edges from face A (face 4 shouldn t exist anymore as you substrated it with face 1)
send me the dbs file

Zweeper April 9, 2009 04:34

on your email adress?

-mAx- April 9, 2009 06:20

upload it on www.rapidshare.com

Zweeper April 9, 2009 06:31

okay, here it is:

http://rapidshare.com/files/219227546/working.rar.html

-mAx- April 9, 2009 08:31

ok I don't understand why it has failed with my previous method, but anyway you can handle your problem followings:
*substract face2 with face 1
*then split the face 2 (which is the result of the previous operation) with face 4
That's it
;)

Zweeper April 9, 2009 10:34

yes, this works! thanks a lot!!!

Zweeper December 20, 2009 14:12

okay, now i have the SAME problem, just for 3D.

I tried the same to solve this issue, but seems like that something with the mesh IN the interior doesn't fix. when i say fluent to show me "just the velocity vectors of the interior", it shows me just vectors on the wall of the interior.
The interior is not filled with vectors. I guess that this is wrong, but i don't know what my mistake is.

any ideas/help for my problems?

Kind regards!

-mAx- December 20, 2009 14:16

post a picture

Zweeper December 20, 2009 14:36

3 Attachment(s)
okay, picture 1 shows my gambit work. the round hemisphere is the interior.
the two bricks in the middle are the walls.

picture 2 shows the bricks (lorry) in fluent. seems like everything is all right!

picture 3 shows now the interior and i have just vectors on the surface of it. is this wrong? i think so, but what could be wrong?


when i want to see the vectors of the standard interior then it shows me all vectors, i mean, then it is okay.

-mAx- December 20, 2009 14:45

in gambit, click on the icon (next to examine mesh)
you will have blue colors instead of green (and pink for the hemisphere).
post the picture.
You should have difficulties to mesh your domain because of the small angle between the big brick and the hemisphere.
What should be th functionnality of the hemispherein comparison of the big brick?
Create a XY plane, and display any variable (velocity for instance), and post also the picture

Zweeper December 20, 2009 15:00

1 Attachment(s)
okay, here is the picture with the specific color mode.

the task of the hemisphere is... its just that we had this more or less in the lesson. the teacher said to us we should create an interior (what sounds logical) and he did it with a hemisphere.

maybe its better to take a big box instead of the hemisphere?

Zweeper December 20, 2009 15:04

1 Attachment(s)
but maybe this is also a problem:

when i mesh the big box, this error message appears (attachment)

when i mesh it a second time, gambit refines the mesh and everything seems like okay. is this a problem? i'm not sure with this.


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