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[ICEM] How to generate this kind of mesh?

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Old   October 3, 2012, 13:43
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A CGrid is really the best kind of grid for a problem like this... It is like having a super thick boundary layer, very efficient and great for Navier Stokes. It is also pretty easy to do (and there is a youtube video with the steps).

The tricky part is the region between the wing tip and the far field wall.

It will likely consist of a rectangular block in the leading edge and a triangular block in the trailing edge.

The rectangular block will have trouble fitting to the curved leading edge of the wing tip. You will either get wide angle elements or need to put an Ogrid block in there, which will still give you bad quality (but better). However, if you sweep it with a paved mesh, you gain alot of freedom. Similarly, the trailing edge block will have a lot of sliver elements as the mapped block is collapsed. There isn't really a good fix for that... I guess you could use a quarter Ogrid, but you will still have pain. A swept block is an easy fix for that also.

Basically, you start with a regular blocking and then change those two blocks to swept at the end...

If you get your hands on R14.5, you can even specify to use the gambit paving algorithm, which is a bit better than the ICEM CFD one for this sort of thing.
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Old   October 3, 2012, 13:55
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Quote:
Originally Posted by PSYMN View Post
A CGrid is really the best kind of grid for a problem like this... It is like having a super thick boundary layer, very efficient and great for Navier Stokes. It is also pretty easy to do (and there is a youtube video with the steps).

The tricky part is the region between the wing tip and the far field wall.

It will likely consist of a rectangular block in the leading edge and a triangular block in the trailing edge.

The rectangular block will have trouble fitting to the curved leading edge of the wing tip. You will either get wide angle elements or need to put an Ogrid block in there, which will still give you bad quality (but better). However, if you sweep it with a paved mesh, you gain alot of freedom. Similarly, the trailing edge block will have a lot of sliver elements as the mapped block is collapsed. There isn't really a good fix for that... I guess you could use a quarter Ogrid, but you will still have pain. A swept block is an easy fix for that also.

Basically, you start with a regular blocking and then change those two blocks to swept at the end...

If you get your hands on R14.5, you can even specify to use the gambit paving algorithm, which is a bit better than the ICEM CFD one for this sort of thing.
Confused....are you talking all this for Hexa Blocking or with reference to Multizone?
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Old   October 3, 2012, 14:03
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The line between can be blurred...

But I am talking about starting with top down hexa and then converting block types, not bottom up multizone from surface blocking.
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Old   October 3, 2012, 14:35
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cfd seeker,
Look at this threak, Hexa + Tetra meshing (Hybrid) in ICEM i sometimes pin the thread that i find useful, may be this one is, look at reponse number 5.
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Old   November 20, 2012, 13:57
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Quote:
Originally Posted by BrolY View Post
Blocking -> Edit Block -> Convert Block Type

That should work !
that does not work. i've been trying to convert a mapped block to free hoping this improves the quality of the mesh but icem prints a message that reads "could not convert degenerate hexas to free no block number 217 found". i don't understand this message since the block 217 is there.
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Old   November 21, 2012, 11:47
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Originally Posted by cesarcg View Post
that does not work. i've been trying to convert a mapped block to free hoping this improves the quality of the mesh but icem prints a message that reads "could not convert degenerate hexas to free no block number 217 found". i don't understand this message since the block 217 is there.
Are you trying to mesh the wing with multizone feature ???
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Old   November 21, 2012, 11:56
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Quote:
Originally Posted by diamondx View Post
Are you trying to mesh the wing with multizone feature ???
i'm trying that since it seems the only way to improve the quality of the elements in the degenerate hexa block located at the sharp trailing edge of the airfoil section.

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Old   November 21, 2012, 12:08
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from my personal experience multizone is very picky when i comes to geometry. before perfoming the build topology, you will need a neat geometry, it is also a new feature in ICEM . it is full of potential but i have always failed to use it with complicated geometries.
After taking a look at your wing, the automatic surface blocks can't generate 2d block in the wingtip. in the other thread i saw that you did a blocking, the attached blk file gave me nothing, would you mind re-sharing it again. could you get good block using the multizone features on you wing ??
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Old   November 21, 2012, 12:18
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You must create the Ogrid around the wing + winglet and your topology looks good now. Then you can use the collaspe command to account for the sharp trailing edge. But use the collapse command after creating the O-grid around wing and winglet.
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Old   November 21, 2012, 12:20
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please refer to this post where i shared the files.

Unstructured "all quad" mesh in ICEM Block Method
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Old   November 21, 2012, 12:25
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Far,

I tried that but I get triangular elements where I collapsed the blocks. The quality analysis tells me that I have inverted blocks near this region.

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