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detached faces on inclined planes

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Old   December 5, 2014, 17:24
Default detached faces on inclined planes
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Diego
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Greetings,

While trying to set up external aerodynamic simulations using snappy
I noticed that my wing surfaces were turning out bumpy.

After playing with simpler geometries a bit, I isolated this very
simple case that exercises such bad behavior: a tilted box inside
a blockMesh-ed wind tunnel. If I don't add boundary layers the
bumps are stuck to the box. Here with three boundary layers you
can see them flying above the surface of the box on the left edge
(also along the front edge, but those are more difficult to spot).



I'm wondering if I'm doing something obviously wrong, or is
this likely to be a bug in snappy?

Best,

--diego
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Old   December 6, 2014, 21:35
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Update: false alarm, I am now fairly certain this is actually a bug in paraview.
When I run the flow, the detached patches don't seem to act like a wall, so the
parsimonious explanation would be that paraview erroneously assigns some of
the internal mesh faces to the patch.
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Old   December 7, 2014, 17:08
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Bruno Santos
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Greetings Diego and welcome to the forum!

Just a quick question/answer - Try following the instructions given here: http://openfoamwiki.net/index.php/FA...is_in_ParaView - if following those instructions you still see these floating triangles, then you might want to check with checkMesh to see if the mesh is sane or not:
Code:
checkMesh -allGeometry -allTopology
Best regards,
Bruno
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Old   December 11, 2014, 22:18
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Diego
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Thanks for the tips Bruno. You were right of course, the mesh ended up broken
after layer addition.

I have since turned my attention to cfMesh and am getting beautiful boundary layers
this way but the simpleFoam solver tends to blow up with these meshes even with no
boundary layers. If you can offer any clues to why this might be, please do!

Thanks,
Diego
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Old   December 13, 2014, 17:19
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Hi Diego,

Quote:
Originally Posted by n719z View Post
but the simpleFoam solver tends to blow up with these meshes even with no boundary layers. If you can offer any clues to why this might be, please do!
Uh... OK, here's a clue: 42

Yes, it's a clue
But a better answer is this - Please follow these instructions: How to give enough info to get help

Best regards,
Bruno
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Old   December 14, 2014, 01:43
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Quote:
Originally Posted by wyldckat View Post
But a better answer is this - Please follow these instructions: How to give enough info to get help
Yup, after some more wrestling with it I finally broke down and uploaded entire case directories to this thread:

Controlling y+ values with snappyHexMesh?
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