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[ICEM] Holes in the prism layer

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Old   September 10, 2013, 20:55
Default Holes in the prism layer
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Alessandro
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Hello everyone,
I have to do an unstructured tetra mesh of an entire airplane but it is giving me a lot of trouble.
I'm using the bottom-up method, so surface mesh -> prism layer-> volume mesh.
I need to create a prism layer that has a height of 2. What I'm trying to do is generate one single layer and after split it. But how you can check from the images below, near the winglet and in other parts of the plane, there are some holes.
The geometry it's ok, all the lines are red.

Winglet clean surface
https://www.dropbox.com/s/zu32dm2vf3ykx2k/Immagine4.jpg
Winglet 1:
https://www.dropbox.com/s/p321b126ze0osnm/Immagine.jpg
Prism layer over winglet:
https://www.dropbox.com/s/1nt7lih02upoxkf/Immagine5.jpg
cut plane Winglet:
https://www.dropbox.com/s/quz5ujgpntfq6c3/Immagine6.jpg
fin and fuselage:
https://www.dropbox.com/s/8uk613raeq2u0zi/Immagine2.jpg
Fin-fuselage-tail
https://www.dropbox.com/s/jn6a7du7q7ifymq/Immagine3.jpg
Prism Parameters:
https://www.dropbox.com/s/5b4b85j9kjwafzw/Immagine7.jpg

fort the smoothing options, I've just "max directional smoothing steps=3" and "first layer smoothing steps=1"

I have also tryed to create a more layer at the same time, but it doesn't work.
The same if I create the prism layer after the volume mesh

1. regarding the winglet, the problem should be that there isn't space enough to create a prism layer with a height of 2 (Indeed I tryed to create a PL with a height of 1 and it works). Is there a way to solve that problem or I have to modify the geometry, filling the little space between the vertical surface (winglet) and the orizontal ones (wing)?

2. Regarding the other parts of the airplane, any particular suggestions?


Thank you.
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Old   September 11, 2013, 09:22
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siw
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I've used ICEM tetra/prism to mesh full aircraft geometies I would say the surface mesh at the winglet region is too coarse. I suggest making that finer and then floating the prism layers (i.e. set the initial height and total height to zero for a few layers) then split and redistribute. Make the prisms after making the volume mesh, the latter with the Delaunay (TGlib and Use AF options on). Remember to check and smooth the surface and volume mesh before making the prisms. Also you can save time with a smoothed volume mesh by setting the volume smoothing in the prisms menu to zero. Also you should switch on the auto reduction option in the prisms advanced options. I would ignore any target prism layer height (e.g. you say 2) and aim for making a mesh and running the CFD solution to check the yplus and resolution of the boundary layer. If you need improe yplus and boundary layer resolution from the CFD solution then alter the surface mesh (which controls the floating prisms) and the prisms split/redistribution.
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Old   September 12, 2013, 05:26
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Alessandro
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hi siw, thank you for your answer
The fixed heigth comes from previous simulations that the person befor me did (I'm continuing him works, but on a very very similar geometry).
Anyway I'll try to do how you said, hoping that it'll works.

Thanks
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Old   September 12, 2013, 06:08
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siw
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You should look at this topic: prism generation.

PSYMN gives a hyperlink to a very useful ANSYS presentation for ICEM prism generation. I use this for guidance alot for my Fluent and CFX simulations.
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