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-   -   [ICEM] improve quality in 3d wing (http://www.cfd-online.com/Forums/ansys-meshing/115318-improve-quality-3d-wing.html)

FJSJ March 28, 2013 04:46

improve quality in 3d wing
 
4 Attachment(s)
Hi guys,

I wonder how I can improve the elements near the trailing edge in the attached photos of a profile is not symmetric. I've thought about moving the rear vertical edge forward to avoid sharp angles ...

Far March 28, 2013 06:19

collapse rear block if trailing edge is sharp. First you should create C-block instead of full o-grid

FJSJ March 28, 2013 07:48

Thanks Far. It is the same strategy as in this video:

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

but why do not you collapse the blocks on your video?

http://www.youtube.com/watch?v=mgjRT4WY_iA

you have a sharp edge too... it's because it is a symmetrical profile?

Far March 28, 2013 08:36

If take a look at thread http://www.cfd-online.com/Forums/ans...mesh-wing.html you will notice there are four methods of dealing wing meshing. So in video it is one the methods described in above thread. If wing is not too sharp, you can continue with your present method.

Hybrid March 28, 2013 12:35

Is block collapsing possible in multizone meshing? AS the quality on the wing with sharp TE is very low nearly 0.0.

Far March 28, 2013 12:37

Hybrid :

Finally you found a method to make the hybrid mesh in ICEM CFD ;)

Can you please share your experience with us on a sample geometry...

Hybrid March 28, 2013 17:37

Visit the link:

http://www.cfd-online.com/Forums/ans...tml#post417081

FJSJ April 10, 2013 04:55

Extrude features
 
3 Attachment(s)
Hi again,

I've been taking a look at the following thread, Hexa Structured Mesh on Wing, and I've seen the 4 meshing methods. For a profile with sharp trailing edge is better collapse blocks. For that reason, I tried that approach previously with the same example I īve written in post # 1 but I got errros. Therefore I would like to clarify some doubts.

1š - In this thread, Hexa Structured Mesh on Wing, Hybrid said you could extrude a face from a 2D block (# 11), however, I think you can only extrude block faces from 2D and not from 3D. Then, Simon said that to do this you have to use "Convert 2D to 3D", which I think is more correct. Once done, if you could use "Extrude Face"... itīs possible.

2š- In image 1 presents the domain. I want to mesh this section and them I want to extrude along the domain. So I think a block 2D planar. This always appears in the middle section of the domain. If this block transfer 2d to the final section (image 2) and active ORFN why I see bend blocks, I`ve tried to compare it with the FAR videos but do not understand why I get bent blocks (image 3). Itīs like the first reference in this blocks or something similar?

FJSJ April 10, 2013 05:01

5 Attachment(s)
3š- If you want to do the mesht in the middle section and then to convert 2D to 3D to one side (image 1) and then extruded to the other side (image 2) works. Then merge blocks and I got this (image 3). However, if deselected "whole blocks" appear again as if they were separate (image 4) . Anyone know why?

FJSJ April 11, 2013 04:51

1 Attachment(s)
Iīve got the mesh. I have done that blocks from 2D Planar blocking and using Convert 2D to 3D and Extrude Faces. The worst determinant 3x3x3 is 0.5, min quality is 0.5, min angle is 40.5 and the max value of vol. change is 6.

I know that way is more work but I wanted to check this way and associate doubts. For that reason, if you could comment the last 2 post Iīll be grateful.
I would know, why concluded Far that the best flow domain is hemisphere in L.E. and rectangular at outlet (#29 Structured Hexa Mesh on Wing).

For other hand, Itīs recommended disassociate from geometry when you extrude a block and then associate again?

FJSJ April 15, 2013 03:20

can you tell me something about these questions, please!

Far April 18, 2013 03:18

In fact when I said the hemisphere domain is best was due to fact that the leading edge is circular and mesh would have the less distortion. But you can use rectangular domain at inlet as I have shown it many times.

Same goes for trailing edge. But one must be careful if trailing is too sharp, in this case you need to collapse blocks and mesh lines becomes parallel to airfoil chord. so if you rounded domain at outlet then you will have high distortion at outlet boundary when straight mesh lines will meet round boundary.

As far as extrude method is concerned, it is generally not recommend for entire model. You can few portions blocked with this method if deemed necassary otherwise always use top-down approach as it saves you alot time and which is basic advantage of ICEM. It saves you huge amount of time on complex models due to top-down approach.

FJSJ April 18, 2013 03:48

Thank you for your answer.

Are very helpful to me. But Iīm still wondering about one... the second one (2š). I not finish to understand it. I donīt know if you can understand it what I ask. I looked your video "Sphere cube meshing : Part I - ICEM CFD 14.0 Basics" for explain about VORFN blocks but at the end I couldnīt find my doubt.

For other hand, Iīm dealing with this problem

Quote:

if you rounded domain at outlet then you will have high distortion at outlet boundary when straight mesh lines will meet round boundary.
and I think I get a good blocking strategy for that case. I want to check it before I explain here.

Far April 18, 2013 03:56

Can you explain a bit more about your doubts with VORFN blocks?

FJSJ April 18, 2013 04:21

3 Attachment(s)
Sure.

Ok. I have a domain like the picture 1. Itīs a 3D domain. Now.. (lf I would like to do this domain with an extrude) I do a 2D planar blocking and this 2D planar block appears in the middle of the domain. So.. like I want to do an extrude I associate edge to curve (the 4 edges, I said this cos in the picture Iīve only put 3 arrows) and now the edge are in one side of the domain (this way I can do the extrude more easily) (picture 2). And now, Iīm wondering... if I turn on VORFN part.. I can see them (VORFN blcoks) but.... they are refered to the initial place, I mean, in the center of the domain (picture 3). why? Why do they go to the same side that I īve associated them before?

FJSJ April 18, 2013 04:34

4 Attachment(s)
I have to say that I got the mesh. This method worked.

But, I would like to say something about associate edge when someone make an extrude too. I had to disassociate the edges and them re-associate them.
is it recommendable to do this when you use an extrude? This was my result.

for better visualization here the project files:
https://www.dropbox.com/s/rhlwsvxnmq5swpg/Project1.rar

Far April 18, 2013 04:37

Quote:

if I turn on VORFN part.. I can see them (VORFN blcoks) but.... they are referred to the initial place, I mean, in the center of the domain (picture 3). why? Why do they go to the same side that I īve associated them before?

Generally speaking VORFN blocks are not important and work internally as designed and are always there. Their internal working is not discussed anywhere. But I showed something how they behave in some situations.

FJSJ April 18, 2013 09:06

Ok. Understood. I just want to know why this behaviour.
Thanks equally!

Far April 18, 2013 09:56

which behaviour?

FJSJ April 19, 2013 03:25

When I said behaviour I want to say the same in post #15. But youīre right.. itīs an internal working. Thanks for youtubeīs videos about this topic :-)


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