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Hannah liang August 26, 2002 14:24

mesh space
Hi, when I write a def. file, the error message come out on which it says the volume mesher cannot produce elements in some area(the coordination given for points which have the problems), and requiring me to produce the mesh space in that area. Who knows how to do that and how to reduce individual mesh space in CFX5.5.1?



Astrid August 26, 2002 16:24

Re: mesh space
I get this message when my geometry is narrow and I apply thick inflation layers (prism elements). Then the mesher has a hard time in creating the volume mesh (hex mesh) between both inflation layers. What helps is either using smaller inflation layers or reducing the mesh spacing.

When you have trimmed surfaces that are curved, it usually helps to use the AFI surface mesher instead of the default Delauney mesher.


Dave August 27, 2002 08:26

Re: mesh space
HI Hannah, Like Astrid said the error will be due to either poor mesh aspect ratios or just insufficient mesh spacing. We have found that this can be a problem when using inflation where the inflation height is too high. Imagine 2 parallel flat plates close together. If you use too large an inflation layer on both plates, then the tetrahedral mesh that must be situated between the inflation layers may have top be very small to fit in the gap. One quick (but not always the best!) way to try and get your mesh to work is to copy the coordinates from the error message, create a point at that location, then create a mesh control on that point. It can also be a wise move to view the mesh on the surrounding surfaces (use the verify option in the meshing form) close to where the error message highlights the bad mesh element. We have often found that a poor surface mesh will be the cause of problems when creating a volume mesh. Does the error message highlight where the poor element is ?? try turning on and off the highlight option on the error form, this sometimes shows where the porblem lies. Hope this helps Dave

Hannah liang August 27, 2002 11:53

Re: mesh space
Thanks Astrid and Dave. That's true. I often simulate the very narrow pathway of the air. If I use the mesh control in those areas, I still have to struggle to adjust the space. Oh, very discouraged! I will try to use AFI.

Thanks very much


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