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[ICEM] How to improve this grid for turbine blade?

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Old   July 1, 2015, 17:53
Default How to improve this grid for turbine blade?
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mosi
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Hi everyone,

I have generated a hexahedral grid for my turbine blade using ANSYS ICEM. I was wondering if anyone could give me some tips on how to improve this grid. I have attached photos from the grid.

My major problem is there are some elements with very low Jacobian (determinant). Not negative, but less than 0.1. These low Jacobian elements appear when I reduce the size of the boundary layer grid over the blade surface. So, how can I have fine boundary layer grid without creating low Jacobian elements?

Also, if there is any way to improve the blocking, etc please let me know.

Thanks,
Mosi
Attached Images
File Type: jpg 3D.jpg (101.8 KB, 49 views)
File Type: jpg Front.jpg (80.1 KB, 43 views)
File Type: jpg TE.jpg (87.4 KB, 41 views)
File Type: png blocking.png (67.8 KB, 40 views)
File Type: jpg quality histogram.jpg (40.3 KB, 37 views)
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Old   July 2, 2015, 04:37
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Eduardo Hoefler
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Hi Mosi,
much could be corrected only by moving control points. But a little awkward is the only describe necessary steps. Send me *.tin and *.blk fails of the case.
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Old   July 2, 2015, 18:05
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Hi hefy,

Thank you for your reply. I have attached the tin and blk files.

Thanks,
Mosi
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Old   July 6, 2015, 04:56
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Hi Mosi,
I had a good will to fix blocking of your case. Finally I came to the conclusion that it is better that I send you a good example how to make a good grid. Send me your e-mail, and then I will try to allow public access to my files. This is an example of the radial turbine stator vane (16 vanes, Z is axis of the machine). The point is that both periodic surfaces should be adapted to the planned blocking.
Otherwise, I suggest that in cases of the rotor or stator turbine blades use Ansys TurboGrid to provide hexa grid, if you have this option. Examine guidelines and examples.

Regards,
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Old   July 6, 2015, 06:48
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Hi Mosi,
I managed to postpone my study case of blocking. Follow the link:

https://www.dropbox.com/sh/bksznjhbs...oo6lLoS7a?dl=0

A lot of success in further work.

Regards
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Old   July 6, 2015, 18:30
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Dear Hefy,

Thank you for your reply's. Unfortunately the dropbox link that you shared does not work. Please email me at: ghoreyshi.mos@gmail.com

Unfortunately, I do not have access to TurboGrid. With regards to the periodic surfaces, I did not quite understand what you mean. I think CFX is able to apply periodic boundary conditions on 2 surfaces even if their grid do not match exactly.

Thanks again for your help. I look forward to your files.

Mosi
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Old   July 8, 2015, 06:10
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Hello All,
This is corrected link up to this file:

https://www.dropbox.com/s/8bvlvhr0mv...ialGV.zip?dl=0

Thanks
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Old   July 9, 2015, 16:09
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Dear Hefy,

Thank you for your files. This is a pretty good blocking and mesh. But you also have some elements with low determinant (I have attached the picture). I guess at this point there is no need to worry about those elements as I have tried my grid with CFX and it converges and generates reasonable results. I can also use some of the techniques that I see in your blocking to improve mine.

One of the points that you said and I wanted to mention again is, as I have understood, CFX can apply periodic boundary conditions on 2 surfaces even if their grid do not match completely (Fluent cannot do this). So if we are using CFX for simulation, I think it is not necessary to apply periodicity in the grid generation process. What do you think about that?

Thanks,
Mosi
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Old   July 10, 2015, 10:05
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Eduardo Hoefler
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Hello Mosi,


I see you've noticed some deficiencies in the blocks in case of my GV. All this can be corrected by fine tuning of the position of vertices.
A few clarifications about the periodicity: If we define the periodicity of the side surfaces of the channel of single vane/blade, then ICEM automatically generates a circular periodic mesh.
In this way in CFX, the meshes of individual vanes are glue together into a comprehensive mesh of the entire rotor domain. Take these steps in ICEM:
> Edit Blocks > Periodic Vertices
> Pre-Mesh Params > Edge Params > Copy It All Parallel Edges
In the case that the flow is calculated in only one stator channel, periodic mesh is not required.

Have much joy in the future work,

Regards
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Old   July 13, 2015, 14:33
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Thank you. Good luck to you in your work as well.

Regards,
Mosi
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Old   July 16, 2015, 08:17
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Hi experts,

I am new in ICEM,
I am working on a high twisted blade and want to generate a hexa mesh on it. I have blocked the geometry but when I defined edge-param and updated all, pre-mesh preview turned to a mess!

first of all, I need recommendations and tips on the generated block. ICEM generates unexpected grids specially in the space between blade tip and shroud. Is there any problem to do with edge associations?
then, why ICEM overrides the user-defined parameters (No. of Nodes on edges)?

attachments are images of the generated grid and blocks which may help.

thanks in advance,

edges.JPG

blocks.JPG

pre-mesh.jpg
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