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Old   October 28, 2016, 05:38
Exclamation Snubber-Mesh-Generation
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Hi all,

i have been trying to generate a mesh with a circle-shaped snubber but after i press "Generate 3D" it just tells me the following:

"Error: could not finish the generation correctly"

In the Terminal it says:
"Error in snubber generation:
Cannot process snubber geometry
Could not sew sheet bodies
Cannot create Blade sheet"

I have used ZR Polylines vor the Meridional Curve Up and Down.

May one of you guys help me?
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Old   October 28, 2016, 17:31
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Holger Dietrich
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Hi Jhob,

The snubber configuration is only available:
- with default topology, matching and not staggered
- with the same streamwise number of points imposed on both blade pressure and suction sides
- with double rounded blade

Can you confirm that this the case in your project? May I ask if you already worked through the Advanced Tutorial 7 "Snubber Control" and read the user manual (Meridional Control -> Mesh Control -> Snubber Control)? As the snubber is a new feature unfortunately I am afraid I can barely give you further advise without having access to your case files.

Kind regards
Holger
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Old   November 27, 2021, 16:48
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Mohammad Mehdi Tokhmehchian
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Hi, I have a problem either. I made a mesh which includes LS steam turbine blade with snubber, there is no negative volume according AutoGrid(Capture3). Then I imported that mesh into CFX and started simulation. As you can see in Capture2 there is at least one negative volume which has not been considered by AutoGrid but CFX makes error.(Capture1 is the position of negative volume). Can you help me with that to refine or solve the mesh?
Attached Images
File Type: jpg Capture3.jpg (112.0 KB, 12 views)
File Type: jpg Capture1.jpg (62.6 KB, 10 views)
File Type: png Capture2.PNG (36.2 KB, 9 views)
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Old   November 29, 2021, 04:25
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Even if AutoGrid does not report negative cells, it looks like the mesh has extremely small angles that can easily be considered negative depending on the calculation method. So it would be good to look at the cause of these very skew cells and fix their cause. Even if the mesh would not have negative cells, it would probably still be problematic to have cells with angles smaller than 1 for example.

From Capture 1 it is difficult to see where exactly the skew cells are located, and what is the mesh topology in that region. Could you please share some more detail?
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Old   November 30, 2021, 04:57
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Mohammad Mehdi Tokhmehchian
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Thank you for your response, I will upload images from settings I used in AutoGrid and a better image from negative cells in mesh. How can I change or refine skew cells in AutoGrid? May I use another software?(1 to 5 images are AutoGrid setting which I used)
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File Type: png 1.PNG (38.7 KB, 5 views)
File Type: png 2.PNG (47.7 KB, 7 views)
File Type: png 3.PNG (30.7 KB, 5 views)
File Type: png 4.PNG (56.7 KB, 4 views)
File Type: png 5.PNG (48.6 KB, 2 views)
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Old   November 30, 2021, 05:01
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Mohammad Mehdi Tokhmehchian
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All negative volumes are in snubber section of mesh according to images: mesh1, mesh2 and mesh3.
Sorry I could not post more than 5 images at a post.
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File Type: jpg mesh1.jpg (24.8 KB, 6 views)
File Type: jpg mesh2.jpg (31.0 KB, 10 views)
File Type: jpg mesh3.jpg (30.7 KB, 6 views)
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Old   November 30, 2021, 05:12
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It may be easier to see what is happening if you look at the mesh on ijk-surfaces in AutoGrid itself. Just look for the block(s) with the lowest angles and scroll to the block in i, j and k-direction to look at the mesh around these poor quality cells.
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Old   December 2, 2021, 11:09
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Mohammad Mehdi Tokhmehchian
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Thanks for your help, I checked the mesh again and found something new which may caused the negative volume. According to image 1, snubber face extends over the periodic face and also there is face twist in contacting points. I don't understand how it can be happened while AutoGrid generated these faces. How do you think about that? How can I fix it?
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File Type: png image1.PNG (154.5 KB, 8 views)
File Type: png image2.PNG (118.2 KB, 5 views)
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Old   December 6, 2021, 06:36
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It looks like something went wrong with the geometry definition. It is really difficult to see what exactly is the cause so I would rather recommend you to contact your local support contact and ask for a check on your project.
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