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[ICEM] Problem with holes in surfaces

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Old   November 7, 2014, 06:54
Default Problem with holes in surfaces
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Robert Bischof
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Hello there,

I have problems with surfaces in icem cfd.

For the k-epsilon simulation, I didn't need to resolve the inflation layer. So the mesh was coarse for wall distance.
Now I want to change to SST turbulence model and so I need to resolve the inflation layer and a low wall distance.
By refining my mesh it becames bad quality. I investigated the bad region and I found a problem with my surfaces. There are Holes in my Geometry. I think, the surface can't follow the spline I imported.
I import only curves from NX and built the surfaces on my own.

Is there a way to avoid this problem ?
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File Type: jpg holes_geometry.jpg (10.6 KB, 18 views)
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Old   November 7, 2014, 09:57
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Robert Bischof
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Another Example at the edge of two surfaces.
The Elements are very small, because of a low wall distance in both direction.

You see, that there will be strange Elements, with bad quality.
There are only a few Elements, but its only at the regions, where the wall distance is very low ?
Are there problems in icem ?

I think, I'am not the first, who try to get a y+-value of ~1 ?!
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File Type: jpg surface_edge.jpg (25.5 KB, 14 views)
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Old   November 11, 2014, 03:33
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Robert Bischof
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Can nobody help me ? I still found no solution for my problem ?

Is there a special method for meshing near wall distance to get low y+ ?
Should I always use O-Grid method to mesh this regions ?
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Old   November 11, 2014, 11:21
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Ludvik Lanicek
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Extend surfaces through together. At intersection of these surfaces create curves. In Blocking for "Edge to Curve" switch ON "Project to Surface Intersection".
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Old   November 12, 2014, 03:59
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Robert Bischof
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I have tried to mesh with you tip, Ludvik, but it makes no difference.

I will give you more details of my geometry. It's a simple pipe. But I need the orange surface, it's my interface to the other part of geometry. Because of that I choose this blocking topology. I need a low wall distance in booth directions, I have drawn the red arrows.


The strange things only happens, when I reach a range, in which the elements will be very small and only at first series of elements. Often at the intersection of surfaces at the edges.

I try to make picture which shows my problem.
For help I will be very thankful. For now I can't find solution.
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File Type: jpg surfaces.JPG (25.0 KB, 5 views)
File Type: jpg blocking_wall_distance.jpg (38.6 KB, 4 views)
File Type: jpg bad_elements.jpg (21.1 KB, 4 views)
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Old   November 12, 2014, 04:38
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Robert Bischof
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I found a solution:

With this thread http://www.cfd-online.com/Forums/ans...y-small-y.html
I activate the setting "Project to Bsplines" and set the "Projection limit" to 0.01.
Now it works fine!
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