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-   -   Why Prism layers don't be created? (http://www.cfd-online.com/Forums/star-ccm/110821-why-prism-layers-dont-created.html)

fshak92 December 21, 2012 11:41

Why Prism layers don't be created?
 
1 Attachment(s)
Hi

In the picture below, you can see the trimmer mesh around an airfoil.
The outer airfoil mesh cells, dont have the 90'degree with the airfoil,Therefore i think it would be good idea to use the prism layers.
I've activated the prism layers but no layers are created neither around the airfoil nor on the block's walls around the airfoil.
Does anybody know why?
I would appreciate also any idea about improving the mesh quality in my case.
(After creating good mesh,it has to be converted to 2d mesh)

Thank you in advance.

LuckyTran December 24, 2012 00:45

By default, prism layers are only generated next to walls. Make sure the airfoil surface is defined as a "wall" otherwise no prism layers will be generated.

fshak92 December 27, 2012 12:17

Quote:

Originally Posted by LuckyTran (Post 398845)
By default, prism layers are only generated next to walls. Make sure the airfoil surface is defined as a "wall" otherwise no prism layers will be generated.

Thank you for reply.But the airfoil surface has been defined as wall and no prism layers are generated...

Paulh December 27, 2012 14:03

Is your image of a section cut through the mesh or of boundaries/walls/surfaces in your model? If you're not showing a section cut, did you turn off prism layers on your domain boundaries?

fshak92 December 29, 2012 09:22

Quote:

Originally Posted by Paulh (Post 399245)
Is your image of a section cut through the mesh or of boundaries/walls/surfaces in your model? If you're not showing a section cut, did you turn off prism layers on your domain boundaries?

No it is not a section cut.Just a picture of whole volume.
I use three volume control and i test most of situations by enabling and disabling the prism in boundaries.But I've got two problems:

1) when i enable 'customized prism' in the volume control surrounding the airfoil, the layers are generated on the outer region of the volume control(there is no wall there!!) .
2) when i leave the volume control values to default, and set the prism layers for my airfoil boundary(or in general for all of my mesh continuum), the layers are created far from the airfoil's surface(between the other meshes),and reducing the prism thickness does not decrease the distance!!

fshak92 January 3, 2013 21:22

Nobody has any idea?
I deleted the volume control, also used Advanced layer mesh and polyhedral mesh but again no prism layers are generated nowhere in my geometry.

abdul099 January 5, 2013 17:28

Please create a section through the middle of your airfoil and post a picture of the mesh in this section.
For me it looks like you've defined the sides of your domain as walls too, right?

fshak92 January 5, 2013 22:27

I found the problem.

By playing with the parameters "layer reduction percentage" and "minimum thickness percentage" the problem was solved.

Thank you all anyway for your considerations.

(To abdul : Yes,first i used "wall" for the sides.But i changed it to "overset mesh" afterwards.
But the problem was solved only after changing the mentioned parameters)

abdul099 January 6, 2013 08:36

Okay, great when it works now.
To share my thoughts: When you set the sides to wall, you don't see the prism layers around the airfoil at the sides since there also will be prism layers created on the sides. Then you might think there are none, although there are prism layers.
You can see that when you create a section somewhere through the airfoil (when the sides are set to wall).

fshak92 January 12, 2013 13:02

Quote:

Originally Posted by abdul099 (Post 400307)
Okay, great when it works now.
To share my thoughts: When you set the sides to wall, you don't see the prism layers around the airfoil at the sides since there also will be prism layers created on the sides. Then you might think there are none, although there are prism layers.
You can see that when you create a section somewhere through the airfoil (when the sides are set to wall).

Dear abdul , i have a question:
Without using any prism layer, i could export it to OpenFOAM and it worked without any problem in mesh.
But after adding prism layers(And consequently using overset mesh for the sides) i got lots of errors in openFoam's checkMesh about having nonClosedCells(particularly around airfoil).
Is there any alternative to "overset mesh" for the boundary condition of the sides? Because it has been added to the newer version of ccm+(7.x) and maybe it has not been defined in the old mesh converters(ccm26ToFoam).
Thank you in advance.

abdul099 January 15, 2013 17:29

Sure. I wouldn't use Overset at all as long as you don't have any overset interface. Why don't you try symmetry plane instead? I mean, when you're running just a small slice of the airfoil, the flow should be more or less symmetric (omitting small scale turbulence phenomena).


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