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[ICEM] Surface mesh does not follow node spacing

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Old   August 20, 2014, 07:32
Default Surface mesh does not follow node spacing
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Robert
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Hi,

I'm currently working on a surface mesh for an aircraft. Therefore I'm using the same approach as the ICEM tutorial of the DLR F6, "Introduction to ANSYS ICEM CFD, Workshop 3.2: Shell Meshing - Winbody". Please find a link to the tutorial attached:
https://www.dropbox.com/s/xy787ex9xs...body_Shell.pdf

Using this approach, I specify the Node Spacing of the curves to setup the surface mesh. Unfortunately my surface mesh does not always follow this node spacing, resulting in a surface mesh that's quite coarse in critical area's (lots of curvature, important flow locations).

How can I force the surface mesh to follow my node spacing?

I've provided a link to my project file:
https://www.dropbox.com/s/qtocrnglym...0SIMP%20V4.prj
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Old   August 20, 2014, 07:35
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I've also made some screenshots to illustrate the situation, although they might be difficult to understand. The green arrow points to a curve node spacing that is followed by the surface mesh, the red arrows indicate the curve that don't.

https://www.dropbox.com/s/zuj5g01wu0...pacing%201.png
https://www.dropbox.com/s/jj8pbzazps...pacing%202.png
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Old   August 20, 2014, 12:49
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Uploading the .prj-file only does not work. We also need .tin, .uns or .blk files.
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Old   August 20, 2014, 13:10
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Sorry mate, that's right. Here they are:
https://www.dropbox.com/s/zqpuyplsix...0SIMP%20V4.uns
https://www.dropbox.com/s/bf43wif02x...0SIMP%20V4.tin
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Old   August 25, 2014, 04:12
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I've been all over my project again, resetting part mesh sizes, surfaces mesh sizing and finally the node spacing again. Not much seems to change. The cells a the front leading edge of the FLAPS and SLATS are still quite coarse and do not follow the surface closely.

Still I am following the exact same steps as in my tutorial:
https://www.dropbox.com/s/xy787ex9xs...body_Shell.pdf

What am I doing wrong?
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Old   August 26, 2014, 09:26
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Patch dependent meshing needs a nearly perfect geometry. This means that all curves are attached to their surrounding surfaces. There should not be any single curves. Your model has lots of single curves (yellow), so you need a better topology. You can try the repair topology tool. Sometimes it is helpful to delete all points and curves permanently before using it, but then you have to do curve bunching once again.

If you have your model as a CAD model I would load it into Design Modeler and make one single body out of the whole model (if possible). Then read it in ICEM with workbenchreader.
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File Type: jpg tif1.jpg (69.6 KB, 42 views)
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Old   August 26, 2014, 10:05
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Thanks a lot for pointing this out!

It is a very complex geometry, which indeed had problems with the topology. Since I've downloaded it as a STEP-file that consisted out of 200+ parts, I decided to narrow it down to a few parts and then repair the geometry using 'Build Topology' part-by-part.

In the project posted above I didn't repair the part WING yet, since it gave some problems using 'Build Topology'. Still, I thought that the topologies of parts FLAPS, SLATS, BUMP, FAIRING and FUSELAGE were all right?

What tolerance did you use? I reckon that you've tried repair the entire topology?
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Old   August 26, 2014, 11:17
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I have made a screenshot with all the options I used for "Build Topology". Then there is one little gap between some slat surfaces. You can easily find this because there is only one yellow line left. I deleted the surfaces and recreated them manually. You can do this before "Build Topology" or you even should do it.

Now other errors should come only from improper mesh sizes/methods. You should be able to sort them out.
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File Type: jpg tif2.jpg (60.6 KB, 29 views)
File Type: jpg tif3.jpg (95.4 KB, 34 views)
File Type: jpg tif4.jpg (92.9 KB, 25 views)
File Type: jpg tif5.jpg (88.5 KB, 26 views)
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