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-   -   [ICEM] Blocking of 2 cylinders (https://www.cfd-online.com/Forums/ansys-meshing/87127-blocking-2-cylinders.html)

 FrankW April 12, 2011 07:13

Blocking of 2 cylinders

2 Attachment(s)
Hi,
i will mesh 2 cylinders with blocking. The problem is the cylinders have a common intersection point. See the pictures in the attachment.
How should i change my blocking to get the right mesh?

Thanks
Frank

 BrolY April 12, 2011 07:19

I guess you created an O-grid for your 1st (big) cylinder.
Then split your O-grid around the curevs of your 2nd (small) cylinder.
Then, do an O-grid for your 2nd (small) cylinder.

 FrankW April 12, 2011 10:41

2 Attachment(s)
Hi BrolY,
thanks for the fast reply. Can you explain how i split the o-grid around the curves of the 2nd small cylinder. In the attachmet i've finished step 1 at a test cylinder.

Thanks

Edit: I 've attached the geometric files

 BrolY April 13, 2011 08:39

I found 2 solutions, but maybe other users may have other ideas:

1) Create 2 meshes, and do a conformal merge of the 2 meshes.
2) in your blocking, create another split along the 2nd (small) cylinder. Then merge the two nodes at the intersection point. Delete the block along your small cylinder (the one created by the previous split), and associate. At the end, the quality of the mesh will be bad ...

I'll try to figure out another way to have a good mes quality without creating 2 meshes.
Good luck !

 PSYMN April 13, 2011 12:34

Solution

4 Attachment(s)
Hey Frank,

The difficulty here is because the smaller pipe is all the way at the end of the larger pipe. It can be done but it is a minor hassle...

Is this how you need the geometry to be? Do you plan to extend the large pipe anyway or does this represent the end wall of the pipe? If it is an end wall, does the actual model meet perfectly like this or does the larger pipe actually extend a little beyond the small pipe? The more complex the model, the more I would suggest you push these questions.

On the other hand, this is a pretty simple model. So lets just sort it out as it is. We will need to propagate the wedge shape back thru the larger pipe... Can you handle wedges (easiest solution) or does your solver require pure hexa? (Or maybe I should just ask; what is your solver?) I will start with wedges. The pure hexa solution involves replacing the wedge with a Yblock...

The basic approach should be to pretend there is a little lip at the end (I actually copied a point out by 0.1 to make it easier to pretend). You will need to split to capture both sides of the little pipe. Ogrid the large pipe as you did, then also Ogrid the smaller pipe (Select the pipe block and the block just inside the large pipe. Also select the face on the outer end of the small pipe and the symmetry planes.) Then come back and merge away the small edge and its parallel pairs (4 total pairs) back thru the model. This will collapse it into a wedge that goes back thru the model.

Anyway, it only takes 2 minutes (less time than to type this email actually), so here it is.

Run the replay file with the "always update" option to see my steps.

Best regards.

 FrankW April 14, 2011 10:49

2 Attachment(s)
Hi PSYMN,

thanks for your explanations. It helps me fine. The original geometry has similar dimensions and is more complicated. In the attachment are the files. The inlay called MG_Rahmen.. is a porus structure. This part was easily to mesh (MG_Rahmen.zip). My problem is the meshing of the rest of the fluidic part. In the past i used only Anys WB meshing and i'am so not confirm with ICEM. Because the small structures i think i can generate better meshs with ICEM with less elements.
The real stuctures has the same dimensions. And i need an adequate model to compare our Oxygen measurements with the theoretic model. Our Flowrate is moderate, we have a real laminar flow RE<10.

Best regards.

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