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[ICEM] Meshing a pipe with sudden expansion

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Old   March 14, 2015, 15:59
Post Meshing a pipe with sudden expansion
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Farzin
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Hello,
I'm trying to generate a structured grid on a pipe with sudden expansion, using ICEM CFD.
I tried many methods to do that, though I'm new to ICEM.
One of those is to split the block in three part, delete the middle one and associate others individually to pipes with different diameters. Then using O-Grid block split. By doing so I got a bad mesh quality on the expansion area.
Another idea was to keep the middle block after the split. It would be a 2D-like block, on the expansion plane. This time I got a little better quality but still not sufficient, on the expansion plane.
Here is the mesh quality statistics using the later procedure:

Code:
0 -> 0.05 : 301 (1.276%)
0.05 -> 0.1 : 0 (0.000%)
0.1 -> 0.15 : 0 (0.000%)
0.15 -> 0.2 : 0 (0.000%)
0.2 -> 0.25 : 0 (0.000%)
0.25 -> 0.3 : 0 (0.000%)
0.3 -> 0.35 : 0 (0.000%)
0.35 -> 0.4 : 0 (0.000%)
0.4 -> 0.45 : 0 (0.000%)
0.45 -> 0.5 : 0 (0.000%)
0.5 -> 0.55 : 0 (0.000%)
0.55 -> 0.6 : 744 (3.153%)
0.6 -> 0.65 : 246 (1.043%)
0.65 -> 0.7 : 1330 (5.636%)
0.7 -> 0.75 : 2244 (9.510%)
0.75 -> 0.8 : 4188 (17.748%)
0.8 -> 0.85 : 4866 (20.621%)
0.85 -> 0.9 : 3046 (12.908%)
0.9 -> 0.95 : 1768 (7.492%)
0.95 -> 1 : 4864 (20.613%)
And these are figures of the pipe and grid.
PIPE_EXPANSION_ICEM-CFD_1.jpg
PIPE_EXPANSION_ICEM-CFD_2.jpg

Any suggestion would be appreciated,
Farzin
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Old   March 16, 2015, 14:54
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Pascal Balz
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Hi,

I'm not sure if I understood you correctly.

But here's how I would mesh this geometry:
1. Create ONE block for the whole geometry
2. Do a O-Grid Split on the whole block
3. Do another O-Grid Split on the newly created middle block
4. Split all blocks at the expansion edge
5. delete the four outer blocks at the small cylinder
6. Assign edges to your geometry
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Old   March 16, 2015, 14:55
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Ghazlani M. Ali
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start by blocking without including the expansion. then extrude the face... easy like that
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New to ICEM CFD, try this document --> https://goo.gl/KAOIwm
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Old   March 16, 2015, 16:40
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Quote:
Originally Posted by pbalz View Post
Hi,

I'm not sure if I understood you correctly.

But here's how I would mesh this geometry:
1. Create ONE block for the whole geometry
2. Do a O-Grid Split on the whole block
3. Do another O-Grid Split on the newly created middle block
4. Split all blocks at the expansion edge
5. delete the four outer blocks at the small cylinder
6. Assign edges to your geometry
Thank you;
I did it as you suggested and it ended with a good quality of mesh on the expansion plane.
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Old   March 21, 2015, 14:58
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Now I'm trying to do an unstructured mesh on half pipe expansion. I do it in similar way I did pipe expansion.
It gives a good mesh quality, but when I import it in ANSYS CFX, solver says the symmetry planes are not parallel. Actually I found that blocks edges are not exactly on geometry surface [on symmetry plane].
The question is how should I associate blocks edges with curves, which are on symmetry plane?
The picture of geo and blocks is attached and edges which are in question are marked.
HALF_PIPE_EXPANSION_ICEM-CFD_1.jpg
Thanks for any comment
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Old   March 24, 2015, 07:01
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I think I've found the fault.
After associating the radial block edges on symmetry plane with nearby curves on the same plane, it seems alright and the CFX Solver works without any interruption.
But there is a considerable difference between the later model (half-pipe expansion with symmetry plane) and the whole pipe expansion.
The whole pipe result seems to be more accurate and realistic.
I extended this conversation to ANSYS CFX sub-forum, in a new thread.
http://www.cfd-online.com/Forums/cfx...expansion.html
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Old   December 29, 2017, 13:36
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Can you please tell me the step by step procedure for meshing half pipe?
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