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Urgent!! Problems in grids

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Old   May 2, 2006, 03:15
Default Urgent!! Problems in grids
  #1
maoasis
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Dear all,

I have used the Quad-- Pave method with a size function to mesh the ground and then use Coopier method to mesh the whole volume. Here is the photo that have been capped from gambit.

http://ihome.ust.hk/~ma_cwl/Screenshot-1.png http://ihome.ust.hk/~ma_cwl/Screenshot.png

Everything seem to be good and normal. However, when the fluent read it, the girds like this:

http://ihome.ust.hk/~ma_cwl/Screenshot-3.png (z=30) http://ihome.ust.hk/~ma_cwl/Screenshot-4.png (z=150)

There are some additional grids ion the pictures cross NW to SE.

1. Why does these happen? 2. How can I solve it?

Thank you!

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Old   May 2, 2006, 09:33
Default Re: Urgent!! Problems in grids
  #2
Jason
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The gambit slices you were looking at aren't exactly at a constant Z value. It highlights the faces of the cells that pass through that Z value, so all of the faces you were showing are just above the Z value you were trying to show but will fluctuate up and down a little depending on how Gambit smoothed the mesh. What's happening in the Fluent slice is that it's making a cut exactly through the Z value you specified. A slice removes 1 dimension from every object it intersects... therefore if the slice intersects a volume, you get a face, intesects a face you get an edge, intersects and edge you get a vertex... except if it intersects a vertex you still get a vertex... So what you're seeing in those extra lines is that the slice is actually passing through the face. Gambit writes your mesh to 1e-06... I'm not sure what Fluent's tolerance is, but I'm sure it's on the same order. This means if the faces in the NE and SW corners have a difference in height of at least 2e-06 then your slice would have to pass through faces at some point to account for this difference. If you need the mesh to look perfect at these slices, then you have to slice your Gambit geometry and remesh. But there's nothing wrong with your mesh. It's not extra elements, it's just how the existing elements intersect your slice.

Hope this helps, and good luck, Jason
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