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-   -   How do you think CFX-Build? (http://www.cfd-online.com/Forums/cfx/19682-how-do-you-think-cfx-build.html)

David June 9, 2003 18:25

How do you think CFX-Build?
 
CFX-Build almost kill me the desire to be an engineer. I tried to build a drill hole with stell case in it. The hole is 1000m long and the diameter is 9''. In order to save computer resource, I tried to build a cylinder then cut it into quaters. But I got error message when I try to mesh it. Anybody know better mthod to build a model.

Thanks!

Glenn Horrocks June 9, 2003 18:32

Re: How do you think CFX-Build?
 
Hi David,

What error message did you get?

Glenn

David June 9, 2003 18:35

Re: How do you think CFX-Build?
 
Hi, Glenn,

Thank you for your prompt response. The error message is as follows: Error: ------

Problem: Topology error detected in CAD model.

CAD edge referenced 4 times by faces. Result: Model invalid for meshing. Cause: Invalid model. Action: Please refer to the user documentation

"Using CFX-Build, Section 5 Meshing" for

topological limitations, and modify the

model accordingly.

Solid 3.3.3


Thanks

gg June 10, 2003 03:50

Re: How do you think CFX-Build?
 
You have big diference in dimensions (1000m to 9"). Try to use hexa cells in some other mesh package or in CFX-Build if it is possible.

REgards, gg

Glenn Horrocks June 10, 2003 18:23

Re: How do you think CFX-Build?
 
Hi David,

As gg said, your hole is very long and thin so the default tetrahedral mesh will not be very good. You should create a hexahedral mesh of the geometry - if you are using CFX 5.6 you can switch that on by changing the meshing mode. It is covered by the documentation.

If you are still on CFX 5.5.1, it is a lot tricker but still possible to make a hexahedral mesh. There have been postings about doing this on this forum previously.

Glenn

Carola June 11, 2003 11:29

Re: How do you think CFX-Build?
 
Hi David!, you have to separate the case in diferents sections (1000m is too large!), at the same time you need to locate de hole in a ring which belong to the tube. I had the same trouble !.

Take Care

Carola

David June 11, 2003 21:10

Re: How do you think CFX-Build?
 
I really appreciate your help.

I tried to use Patran (in CFX 5.6) to descretize the geometry. Finally I got four domains in the problem. This time errors comed up in Solver. It says:

</n> ERROR #004100018 has occurred in subroutine INMES. | Fatal overflow in linear solver.

</n> I know the aspect ratio for the element is 0.05/10=0.005. Can anybody tell me whether large aspect ratio cause overflow?

Thanks!

David

Robin June 12, 2003 12:38

Re: How do you think CFX-Build?
 
Not likely, as this is not that large an aspect ratio. Check your boundary conditions and verify that the mesh is in the right units (check dimensions in Post).

Robin

David June 13, 2003 16:32

Re: How do you think CFX-Build?
 
Hi,Carola,

Thank you! Did you mean that I can divide the whole geometry along the center of the drill hole into several sections, for example, every 100 m/section.

Regards!

David


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