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Best Association Practice for 3D meshing w/ICEM (associate edge, face, vertices..?)

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Old   January 11, 2012, 11:16
Default Best Association Practice for 3D meshing w/ICEM (associate edge, face, vertices..?)
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Hello,

I am a new user of ICEM struggling with getting my associations correct while generating a 3D mesh in ICEM. I am working on a linear turbine cascade. My geometry is specified through curves for the airfoil using an IGES file. The IGES file only contains the airfoil (no domain walls like inflow, outflow, top, bottom, etc) so after importing the IGES file I then use the geometry generation in ICEM to specify these curves. After doing all this, I have the domain I want specified completely by a series of curves.

I have a pretty good idea about my blocking strategy. I am either going to use a 4HO grid or maybe a shifted periodic grid. In either case though my problem hasnít been getting good mesh quality so much as getting any mesh at all. Iíve tried a few times, but whatever I do I canít get control of all the associations correctly and I end up having a pre-mesh with grid lines overlapping one another, etc.

In my first attempt I tried converting the geometry into surfaces for each part and then associating those to the block faces. I donít remember the full details, but it seemed like sometimes I also needed to associate some edges to curves as well when doing this. The problem there was that the surface edges and the curves were a little outside of tolerance and thus the behavior wasnít as I hoped. I also had some overlapping cells.

For my second attempt I tried solely using curves and edges, but that went even worse. Even when I tried to explicitly set all the associations to the blade and outer walls I still had many overlapping cells/blocks in the pre-mesh. I think a lot of my internal block edges/vertices (ie block edges/vertices that should be in the fluid, not attached to a physical body/boundary) kept getting associated to geometry. I tried removing their associations and only specifying the associations for the outer boundary and blade, but I still had the problem.

Iím sure Iím doing several things wrong, but my biggest question is whether I should be trying to associate completely using surfaces, completely using edges, or some combination of the two (or if it really matters). Should associating a face to a surface be enough, or do you also need to associate the edges and vertices?

Really appreciate any advice people can give. Thanks very much. Sorry for not including screenshots/geometries, but its something I really canít share openly.

Andrew
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Old   February 1, 2012, 04:26
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Sijal Ahmed Memon (turboenginner@gmail.com)
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can you please post some pics
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Old   April 16, 2012, 18:18
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hello Andrew, As far as i understand, the associations are to be used as per the requirements.
Maybe you can change the tolerance value towards the higher side (reduce the decimals). Also check the face association for the faces which are inside the fluid domain (simply disassociate the faces which are/should not be projected to any boundary.
It will be ok to use all of curve , point and surface association, but with care. But it wont always fine to use only one of these.
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Old   April 17, 2012, 14:26
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For twisted surfaces, even when the associations are made ( to curve/ surface) some overlapping is possible...easiest way to rectify it is to split the associated edges...u can use options like linear/auto linear/etc in the edit edge tab.

And face projections are very rarely required in typical situations.
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Old   April 15, 2013, 04:32
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Hi there!

I'm facing a bus shaped body mesh and I have some trouble with the body back... I post some pics here... What would be the correct association to manage the round eges problem??

https://www.dropbox.com/s/ziyzqdsgrh...Back_edges.gif
https://www.dropbox.com/s/pekkq6bvvi...sBack_mesh.gif

Best!!
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Old   April 15, 2013, 05:11
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did you look at the Ahmed body tutorial?


Mesh Quality
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Old   April 15, 2013, 11:55
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you need to associate the outer edge not the inner edges
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New to ICEM CFD, try this document --> http://goo.gl/G2gkE
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