[GAMBIT] Boundary layer direction

Markus · November 7, 2012, 08:39

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, 04:43

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, 06:54

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, 08:32

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??

Marion · November 8, 2012, 10:12

Quote:

Originally Posted by Markus

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, 10:24

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

Markus

Marion · November 9, 2012, 03:17

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, 03:18

Quote:

Originally Posted by Marion

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, 03:53

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, 04:38

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, 11:14

hi

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

Markus

Far · November 9, 2012, 12:10

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, 13:09

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, 13:22

like this.....

Far · November 12, 2012, 05:01

I hope this is helpful to you.

November 7, 2012, 08:39	Boundary layer direction	#1
Markus New Member Join Date: Oct 2012 Posts: 14 Rep Power: 13	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! Last edited by Markus; November 7, 2012 at 08:58.

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November 8, 2012, 04:43		#2
Marion Senior Member Marion Join Date: Jul 2012 Location: France Posts: 122 Rep Power: 14	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.

November 8, 2012, 08:32		#4
nkme2007 Member Tamil Nadu Join Date: Oct 2012 Posts: 44 Rep Power: 13	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??

November 9, 2012, 03:17		#7
Marion Senior Member Marion Join Date: Jul 2012 Location: France Posts: 122 Rep Power: 14	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.

November 9, 2012, 03:53		#9
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	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

November 9, 2012, 04:38		#10
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	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?

November 9, 2012, 11:14		#11
Markus New Member Join Date: Oct 2012 Posts: 14 Rep Power: 13	hi Thank you very much for all the advice, i will try it out. Markus

November 9, 2012, 12:10		#12
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	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?