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Old   March 5, 2013, 10:06
Default Blocking domain and blade
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Javi
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Hello,

I write this post to see if any of you could advise me on the blocking strategy is appropriate. I'm trying to mesh this domain (image1,2)

image 1.JPG image 2.JPG.

Before I do this, I want to split it the whole domain into 3 sections and then mesh them separately. Now I show the first of it (image 3).

image 3.JPG

To be clear what I do in this case attached this video.

http://www.youtube.com/watch?v=TMbkw...ature=youtu.be

I am delighted to tell me what I'm doing wrong or if the strategy is not adequate. I make an o-grid but then if I want to have a sharp trailing edge I have to collapse blocks and I think that worsens the cylinder .. I do not know what would be the optimal strategy.

Thank you in advance
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Old   March 5, 2013, 12:08
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You started well, but i would not have collapsed the block. don't do it . at the end , it's like you are blocking a wing. and there multiple way of doing this. it's up to you. what i will suggest . Just before collapsing the block, or merging anything, look for how to deal with the trailing edge in 3d. there are a lot and a lot of thread about this.
i wish i can help, but i'm busy these days. may be in the week end. you also started some threads before about blocking of wings , how did it go ? can't you apply it for this geometry.
Also, you are splitting your hole geometry in three. how are you gonna reassemble the mesh ??
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New to ICEM CFD, try this document --> http://goo.gl/G2gkE
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Old   March 6, 2013, 04:30
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You're right, it's like a wing, but as in this video

http://www.youtube.com/watch?v=EknKVAJGEJ8

collapse them is not a bad idea if there is a sharp edge. Besides, this piece of blade is twisted ... I don´t know if I´ll get good results if not collaps the blocks.
Thank you for your feedback. Yes, I made those little cases as examples. I've done all the exercises in ANSYS Tutorial Manual but actually before start the actual domain meshing I want to practice with these geometries. Yes, I get the meshing but always remaining elements of poor quality near the trailing edge.
I think I explained wrong. Yes, I separate the domain into 3 parts. But only because I want to mesh them separately, like examples a little more real for my real domain. Then, I want the take the whole problem and mesh it.
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Old   March 6, 2013, 05:14
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http://www.youtube.com/watch?v=TMbkw...ature=youtu.be

Blocking this piece of geometry is very much simple. Just a 5 min job. When you will make the full scale blocking, this approach wont help you much.
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Old   March 6, 2013, 05:51
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Hi FJSJ, I'm doing a similar case of a wind turbine blade with sharp trailing edge. Have you found negative volumes around the blade? I'm practicing with a straight (not twisted yet) NACA cylinder some blocking strategies but I cannot avoid negative volumes even if I get a min quality of 0.4. I've tried both, collapsed and not collapsed trailing block but I've been suggested to use a collapsed one for such a sharp edge. You can see two of my blocking in the pics, both gave negative volumes.
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File Type: jpg naca_cylinder_blocking_001.jpg (30.3 KB, 37 views)
File Type: png Naca_cylinder_collapsed_trailing.png (24.4 KB, 35 views)
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Old   March 7, 2013, 04:36
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thank you for your comment Far. Yes... i´ve been thinking about this. I mean, i can mesh first part of my domain separately but when I have to do the whole domain it isn´t useful. anyway, I'd like meshing, as an exercise to practice. The link you left I think it isn´t works.I would like to see it, if is possible.
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Old   June 25, 2013, 05:48
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Hi, Far.
I am also meshing a twisted wind turbine blade with a sharp trailing edge, and there are a lot of negative element at the trailing part. Would you give me some tips? by the way, I really like to see the video you posted if it works!

Best regards,
Ye
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Old   June 25, 2013, 05:49
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Hi Bollonga,

Did you solve this problem? Now I have the same problem as you. Hope you can give me some suggestions if you have solved it.

Best regards,
Ye
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Old   June 25, 2013, 08:39
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Hi kiddmax,

try to attach some pictures about your geom
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Old   June 25, 2013, 08:46
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Quote:
Originally Posted by kiddmax View Post
Hi, Far.
I am also meshing a twisted wind turbine blade with a sharp trailing edge, and there are a lot of negative element at the trailing part. Would you give me some tips? by the way, I really like to see the video you posted if it works!

Best regards,
Ye
that video is down for some reason, may be deleted.

We solved same issue in another thread and it clearly shows that different topology is required to handle sharp TE

Structured Hexa Mesh on Wing
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Old   June 26, 2013, 05:29
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Quote:
Originally Posted by Far View Post
that video is down for some reason, may be deleted.

We solved same issue in another thread and it clearly shows that different topology is required to handle sharp TE

Structured Hexa Mesh on Wing
Dear Far,

Thank you for your reply.

For now, there is some problem between the sharp trailing edge and the hub. I want to collapse the block at the sharp tailing edge, which result in disorder mesh. Look at my pics.

Meanwhile, I am not very sure about the block Strategies about this geometry. Can you give me some guideline? I can not post my tin and prj file because of exceeding the size

Best regards,
Ye
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File Type: jpg 2.jpg (33.6 KB, 33 views)
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Old   June 26, 2013, 06:21
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I would suggest to give some finite thickness to blade at TE.
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Old   July 2, 2013, 10:44
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did you guys solve the problem at the trailing edge part?
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Old   July 3, 2013, 02:39
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Hi Cesar,

did you watch the video in first post?

It´s not the best solution at all, but.. at least you can think in similar approaches.
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Old   July 3, 2013, 09:30
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Hi FJSJ,

I have not watched the video. I just read some portions of the thread and thought that I may be able to give some ideas with the trailing edge issue.

Regards
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Old   July 3, 2013, 10:21
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Hi Cesar,

Ok.It´s just... thinking about your blocking approach. I think that if you want to get good quality in trailing edge you have to "collapse blocks" (like 8:10 in the next video)

ANSYS 12.1 (Part 2 of 3) ICEM CFD Hexa 2D Airfoil meshing

Take a look to looking for some similar threads. For example, if I don´t remember wrong, there is an very useful approach (at least for me)

Ralen Approach
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Old   July 3, 2013, 10:34
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Yes, I have seen that video many times. I also checked the Ralen approach you are telling me about when I had problems with meshing a geometry for my thesis. It is a very good example that Far recommended me. If you are using a C-type mesh topology, I could say that collapsing the blocks from the trailing edge up to the far field can help you to improve the quality of the cells.

Regards
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