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-   -   [ICEM] Blocking domain and blade (http://www.cfd-online.com/Forums/ansys-meshing/114106-blocking-domain-blade.html)

FJSJ March 5, 2013 10:06

Blocking domain and blade
 
3 Attachment(s)
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)

Attachment 19578 Attachment 19579.

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).

Attachment 19580

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

diamondx March 5, 2013 12:08

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 ??

FJSJ March 6, 2013 04:30

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 donīt know if Iīll 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.

Far March 6, 2013 05:14

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.

Bollonga March 6, 2013 05:51

2 Attachment(s)
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.

FJSJ March 7, 2013 04:36

thank you for your comment Far. Yes... iīve 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 isnīt useful. anyway, I'd like meshing, as an exercise to practice. The link you left I think it isnīt works.I would like to see it, if is possible.

kiddmax June 25, 2013 05:48

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

kiddmax June 25, 2013 05:49

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

FJSJ June 25, 2013 08:39

Hi kiddmax,

try to attach some pictures about your geom

Far June 25, 2013 08:46

Quote:

Originally Posted by kiddmax (Post 435773)
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

http://www.cfd-online.com/Forums/ans...mesh-wing.html

kiddmax June 26, 2013 05:29

1 Attachment(s)
Quote:

Originally Posted by Far (Post 435849)
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

http://www.cfd-online.com/Forums/ans...mesh-wing.html

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

Far June 26, 2013 06:21

I would suggest to give some finite thickness to blade at TE.

cesarcg July 2, 2013 10:44

did you guys solve the problem at the trailing edge part?

FJSJ July 3, 2013 02:39

Hi Cesar,

did you watch the video in first post?

Itīs not the best solution at all, but.. at least you can think in similar approaches.

cesarcg July 3, 2013 09:30

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

FJSJ July 3, 2013 10:21

Hi Cesar,

Ok.Itīs 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 donīt remember wrong, there is an very useful approach (at least for me)

Ralen Approach

cesarcg July 3, 2013 10:34

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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