[ICEM] Blocking domain and blade

FJSJ · March 5, 2013, 09:06

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

diamondx · March 5, 2013, 11:08

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, 03:30

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 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.

Far · March 6, 2013, 04:14

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, 04:51

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, 03:36

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.

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

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

Quote:

Originally Posted by Far

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?

It´s 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.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

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

March 5, 2013, 09:06	Blocking domain and blade	#1
FJSJ Senior Member Javi Join Date: Jan 2013 Posts: 276 Rep Power: 16	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

March 5, 2013, 11:08		#2
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 28	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 ?? __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

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March 6, 2013, 03:30		#3
FJSJ Senior Member Javi Join Date: Jan 2013 Posts: 276 Rep Power: 16	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.

March 6, 2013, 04:14		#4
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	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.

March 7, 2013, 03:36		#6
FJSJ Senior Member Javi Join Date: Jan 2013 Posts: 276 Rep Power: 16	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.

June 25, 2013, 05:48		#7
kiddmax Member Ye Zhang Join Date: Dec 2009 Location: Delft,Netherland Posts: 92 Rep Power: 16	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

June 25, 2013, 05:49		#8
kiddmax Member Ye Zhang Join Date: Dec 2009 Location: Delft,Netherland Posts: 92 Rep Power: 16	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

June 25, 2013, 08:39		#9
FJSJ Senior Member Javi Join Date: Jan 2013 Posts: 276 Rep Power: 16	Hi kiddmax, try to attach some pictures about your geom

June 26, 2013, 06:21		#12
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	I would suggest to give some finite thickness to blade at TE.

July 2, 2013, 10:44		#13
cesarcg Member Cesar Join Date: Nov 2012 Location: Guanajuato, México Posts: 78 Rep Power: 15	did you guys solve the problem at the trailing edge part?

July 3, 2013, 02:39		#14
FJSJ Senior Member Javi Join Date: Jan 2013 Posts: 276 Rep Power: 16	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.

July 3, 2013, 09:30		#15
cesarcg Member Cesar Join Date: Nov 2012 Location: Guanajuato, México Posts: 78 Rep Power: 15	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

July 3, 2013, 10:21		#16
FJSJ Senior Member Javi Join Date: Jan 2013 Posts: 276 Rep Power: 16	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

July 3, 2013, 10:34		#17
cesarcg Member Cesar Join Date: Nov 2012 Location: Guanajuato, México Posts: 78 Rep Power: 15	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