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

mosi · July 1, 2015, 16:53

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

hefy · July 2, 2015, 03:37

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.

mosi · July 2, 2015, 17:05

Hi hefy,

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

Thanks,
Mosi

hefy · July 6, 2015, 03:56

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,

hefy · July 6, 2015, 05:48

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

mosi · July 6, 2015, 17:30

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

hefy · July 8, 2015, 05:10

Hello All,
This is corrected link up to this file:

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

Thanks

mosi · July 9, 2015, 15:09

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

hefy · July 10, 2015, 09:05

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

mosi · July 13, 2015, 13:33

Thank you. Good luck to you in your work as well.

Regards,
Mosi

amin.nbkh · July 16, 2015, 07:17

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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July 2, 2015, 03:37		#2
hefy New Member Eduardo Hoefler Join Date: Jun 2015 Posts: 8 Rep Power: 10	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.

July 6, 2015, 03:56		#4
hefy New Member Eduardo Hoefler Join Date: Jun 2015 Posts: 8 Rep Power: 10	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,

July 6, 2015, 05:48		#5
hefy New Member Eduardo Hoefler Join Date: Jun 2015 Posts: 8 Rep Power: 10	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

July 6, 2015, 17:30		#6
mosi New Member mosi Join Date: May 2014 Location: College Station, Texas Posts: 10 Rep Power: 11	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

July 8, 2015, 05:10		#7
hefy New Member Eduardo Hoefler Join Date: Jun 2015 Posts: 8 Rep Power: 10	Hello All, This is corrected link up to this file: https://www.dropbox.com/s/8bvlvhr0mv...ialGV.zip?dl=0 Thanks

July 10, 2015, 09:05		#9
hefy New Member Eduardo Hoefler Join Date: Jun 2015 Posts: 8 Rep Power: 10	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

July 13, 2015, 13:33		#10
mosi New Member mosi Join Date: May 2014 Location: College Station, Texas Posts: 10 Rep Power: 11	Thank you. Good luck to you in your work as well. Regards, Mosi

July 16, 2015, 07:17		#11
amin.nbkh New Member amin Join Date: Jun 2015 Posts: 5 Rep Power: 10	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