[Far]

I took a look on your case. It is not possible to get good hexa with such angle.

[crostolo]

Hi Far,
I scratch my head on for a while on that geometry. Finally I was able to reach a quality > 0.25 - 0.3

On the tail on the wing section I recreate your blocking strategy (two blocks tangent to for a diamond) and than I select each faces of them and under
edit block --> convert block type --> I chose type Y block and in the image attached you can see how it looks like

If anyone has other advices how to improve the quality, I attach the .blk and .tin files if you want to see (I reckon my blocking is a bit ..messy )

[Anna Tian]

Originally Posted by Far

Method 2

http://www.4shared.com/rar/qXCmda1T/file.html

In this method, O block around wing is created first (blocks collapsed in previous step at trailing edge), then tip block is split into two parts one for leading edge and one for trailing. For trailing edge block with 3 edges, Y-block is inserted. For the leading edge block, O-block is applied. See attachments and Figs.

Now working on method 3, that is not to use the collapse block command and simply creating O-block around air foil assuming trailing edge is also round.

I also tried to generate the mesh in this way. But the problem is the trailing edge angle for my airfoil is lower than 18 degrees (I model the airfoil NACA 2412). So even though you use the Y-block, you still have the smallest grids angle lower than 18 degree. Any thought about this trailing edge angle constraint? How to solve this problem without introducing GGI?

[Far]

Originally Posted by Anna Tian

I also tried to generate the mesh in this way. But the problem is the trailing edge angle for my airfoil is lower than 18 degrees (I model the airfoil NACA 2412). So even though you use the Y-block, you still have the smallest grids angle lower than 18 degree. Any thought about this trailing edge angle constraint? How to solve this problem without introducing GGI?

Collapse the block in trailing edge. And in the trailing edge block converte mesh to free type.

[Anna Tian]

Originally Posted by Far

Collapse the block in trailing edge. And in the trailing edge block converte mesh to free type.

What do you mean by free type? Unstructured grids?

[Far]

yes. It will improve quality in the regions where hexa mesh wont fit...

[Anna Tian]

Originally Posted by Far

yes. It will improve quality in the regions where hexa mesh wont fit...

I tested GGI for different AoA. GGI works well for the wing tip interface (at least for my case). So I have a feeling that actually we don't need those complex grids generation strategy at all.

Another way to solve this problem is to round the very tiny small trailing edge tip. It is widely known in the airfoil aerodynamics that rounding of trailing edge tip slightly won't change its performance and the flow. And also there is manufacturing tolerance. So it can't be perfectly sharp naturally.

[Far]

Yes you are correct.

GGI works fine with new software technology

Sharp angles are possible to manufacture in reality...

[Anna Tian]

Originally Posted by Far

Yes you are correct.

GGI works fine with new software technology

Sharp angles are possible to manufacture in reality...

Yes. Sharp angles can be manufactured. But the radius of the sharp trailing edge will still naturally exist (like 0.01 mm or even smaller). We can just use that tiny radius in CFD. Then we won't have to model the sharp angles and use Y block anymore even though our grids at the trailing edge might have to be very small to capture the radius. But we won't run into any grids quality problem any more. This also reduces the grids generation complexity.

[mrh111]

hi
I tried to generate mesh around wing with winglet in ICEM but after generating mesh the quality of mesh is very low and I give some error in fluent.
3 pictures are attached.
Hope any of you can give me an advice for a better blocking strategy or any other suggestion is welcomed.

http://uupload.ir/files/92i4_1.jpg
http://uupload.ir/files/r4bh_2.jpg
http://uupload.ir/files/nd2n_3.jpg

[niablis]

Hi mrh111, there doesn't seem to be any attached pictures or files.

[mrh111]

is that fixed?

[niablis]

Yes it did!

Ok so I can't tell much from the pictures; nothing is really standing out that would cause errors. It looks like you used an O-grid for the wing, but how did you transition from the wing to the winglet using the O-grid? If I can to guess, it would be that your problem is occurring at the intersection of the winglet and the wing. It is possible to create an O-grid in an "L" shape, which might work better for you.

If you want, you can post your file and I'll look at it over the weekend.

[mrh111]

Originally Posted by niablis

Yes it did!

Ok so I can't tell much from the pictures; nothing is really standing out that would cause errors. It looks like you used an O-grid for the wing, but how did you transition from the wing to the winglet using the O-grid? If I can to guess, it would be that your problem is occurring at the intersection of the winglet and the wing. It is possible to create an O-grid in an "L" shape, which might work better for you.

If you want, you can post your file and I'll look at it over the weekend.

it's very kind of you.i will be really grateful.
http://up.persianscript.ir/uploads2/...-winglet-6.rar
actually i guess i fixed the "L" shape problem. but the quality of mesh is still low
and i get some error in FLUENT.
http://up.persianscript.ir/uploads2/...-winglet-7.rar
http://up.persianscript.ir/uploadsmedia/75f0-44444.jpg
http://up.persianscript.ir/uploadsmedia/75f0-55555.jpg

[niablis]

Hi mrh111,

I took a look at your file. Great job with using the O-grid on the winglet. I did find two problems, however. First, there is an association problem with one of the blocks on the bottom side of the wing near the winglet. See the first attached image. This is very likely causing some or all of your Fluent errors. Secondly, as can be seen in the second attached image, the cells right of the wing have quite a large aspect ratio. I would consider refining them for best performance.

In case you didn't already know, you can find "Scan Planes" in the drop down menu when you right click on the "Pre-Mesh" item under "Blocking". It is very, very helpful when working with structured meshes and blocking.

Hope this helps, and good luck!
-Ben

[Far]

I dont see any curves in geometry.

[Far]

to complete the thread, please see this new part with new method to mesh same geometry.

https://www.youtube.com/watch?v=UO8RJWsIV40

[dariodario32]

Hallo,
I tried to follow this tutorial, but when I try to compute the mesh I have the following error:

Running hexa-dominant mesher...
{expecting 2 shells on edge 18 14 found 4
}
error orienting normals, perhaps there is more than one region
error in output_boundaries
Hex Dominant meshing failed

Could you please check my files?

files --> https://drive.google.com/open?id=0B0...3RFdmV5TzJ5Wk0

Thanks

SOLVED