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-   -   [GAMBIT] Boundary layer direction (http://www.cfd-online.com/Forums/ansys-meshing/109017-boundary-layer-direction.html)

 Markus November 7, 2012 09:39

Boundary layer direction

Hello,

I have a very frustrating problem and i read through so many posts but nothing works.

I have substracted my cubic like geometry from a big cube for the computational domain and now want to create a boundary layer on the inner surface of course pointing to the fluid. But gambit always points it inside ?!?!!

I have read about using the middle button of the mouse, double left klick and to use the list and add the same face until it points the right way.

But it just doesn't work.. :-(

Also i tried defining the space in between as fluid and the structure as solid..

I would appreciate any type of help a lot! Pleeease help me!

Thanks!

 Marion November 8, 2012 05:43

Hi Markus,

Do you have volumes other than your fluid domain in Gambit?
Can you add a picture, it would be easier to understand...

Marion.

 Markus November 8, 2012 07:54

4 Attachment(s)
Hi Marion,

Thank you for answering. I think i only have the fluid volumes. (see pictures 3 and 4)

The geometry in the middle is the thing i want to put in the flow. then thought its good to make a close region for the boundary layer and a fine mesh and then i wanted to fill the rest of the computational domain (volume2) using a size function.

best,
Markus

 nkme2007 November 8, 2012 09:32

Hi Markus,

Mine is also similar problem, I feel. I want to model a building in GAMBIT 3D. Finally, aim of my project is to simulate the temperatures of the walls of building when water flows through pipes inserted in the ceiling (using Ansys Fluent). Is it possible to solve?? :confused:

 Marion November 8, 2012 11:12

Quote:
 Originally Posted by Markus (Post 390976) Hi Marion, Thank you for answering. I think i only have the fluid volumes. (see pictures 3 and 4) The geometry in the middle is the thing i want to put in the flow. then thought its good to make a close region for the boundary layer and a fine mesh and then i wanted to fill the rest of the computational domain (volume2) using a size function. best, Markus
Markus,

Try to split your volumes first, it will be easier to control the mesh.

Is it hollow in the middle? or do you still have a volume there?

If you want, you can attach your model and I'll have a try.

Marion.

 Markus November 8, 2012 11:24

1 Attachment(s)
i think it is hollow... :-)
That would be very nice of you, thanks!

Markus

 Marion November 9, 2012 04:17

Hi,
I've just had a look, and I got the same issue on your original model.
But I confirm my advice: split your volume into smaller domains.
I split it in 8, and I used BL on edges it worked very well :)
As it is a simple geometry, you can even split it on each side of your small parallelepipeds.
I hope this helps,
Marion.

 Marion November 9, 2012 04:18

2 Attachment(s)
Quote:
 Originally Posted by Marion (Post 391162) Hi, I've just had a look, and I got the same issue on your original model. But I confirm my advice: split your volume into smaller domains. I split it in 8, and I used BL on edges it worked very well :) As it is a simple geometry, you can even split it on each side of your small parallelepipeds. I hope this helps, Marion.

Here are some snapshots.

 Far November 9, 2012 04:53

boudary layer is good option, but should be used where it is appliable. Dividing into small volume is the best approach for hexa mshing and mesh control in particular area. For example see this thread http://www.cfd-online.com/Forums/ans...d-channel.html and this video: http://www.youtube.com/watch?v=Gub1Kbcup2k&feature=plcp

 Far November 9, 2012 05:38

How many cubes are there? do you want to mesh inside the small cube, where small sheets are present? Is it part of Fluid?

Do you have access to ICEM?

 Markus November 9, 2012 12:14

hi

Thank you very much for all the advice, i will try it out.

Markus

 Far November 9, 2012 13:10

There are three cubes and some protrusion (six in total)? volume inside the small cube (cube) is hollow? and also volume inside six small box is also hollow?

 Markus November 9, 2012 14:09

1 Attachment(s)
The geometry which represents the solid is the big cube and the six cubes on the surfaces, they are not fluid.

Its a model of a cubesat with thrusters (6 small cubes ) for an underwater test.

I did try by splitting, but it also looks strange now

 Far November 9, 2012 14:22

2 Attachment(s)
like this.....

 Far November 12, 2012 06:01

1 Attachment(s)
I hope this is helpful to you.

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