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-   -   Meshing with CFX-4.2 (http://www.cfd-online.com/Forums/main/641-meshing-cfx-4-2-a.html)

M Bard & C Elmqvist March 15, 1999 20:57

Meshing with CFX-4.2
 
Hello,

we use cfx-4.2 and we are trying to construct a room with a door and a window. We construct our geometry by putting a surface (door or window) on a solid (the room).Our problem is that we get double meshes, how do we avoid this? We do not want to construct it by joining different surfaces or blocks together, since it then will be difficult to modify the geometry afterwards.

Erich Fitzpatrick March 16, 1999 10:34

Re: Meshing with CFX-4.2
 
Hey-

I use cfx-Tascflow, so boundary condition definition may be a bit different; however, I would put the nodal arrangement in one block such that the door could be defined as a boundary condition. Then you have 1 block structure with your door in place (nodally). Same could work with the window. If you can use P-cube to mesh, I know this could be done.

Good luck, Erich

P.S. If you import the geometry in via Iges, you can have construction curves defining the door and window. If you can use face association or similar, the nodes can be made to lie along the construction curves.

Michael Song March 16, 1999 13:47

Re: Meshing with CFX-4.2
 
Hi, You may use constraints (advanced ones if you like to). First, project the curves outlining the window and the door onto the solid. Then invoke constraint functions. Hope it help you.

Michael

David Creech March 17, 1999 13:32

Re: Meshing with CFX-4.2
 
Hi,

While you can use constraints to create the bc's (by creating a face on the block for the room, and then constraining the face to the block) I would recommend simply creating multiple blocks. You can easily modify them later.

Meshbuild (its older than Build, but I find it to be much better) allows you to stretch and otherwise modify blocks after you create them. I have used this approach for some very complex geometries where I wanted to do parametric studies on the model size. I believe you can do the same with the Build program also.

With complex geometries, there are a lot of topology problems that you can run into using constraints. I have found it easier to create good meshes using multiple blocks.

David Creech

CFX User Subroutine Archive

Michael Song March 17, 1999 17:29

Re: Meshing with CFX-4.2
 
Hi, David. Thanks for your follow-up. Concerning with Meshbuild's edge over the new Build in parametrical study, I agreed with you and want to add that CFX support suggested to modify journal file once the model topology is fixed, otherwise ... By the way, I just got out your CFD Website, thank you for your contribution to CFX users.

Regards,

Michael

David Creech March 17, 1999 18:44

Re: Meshing with CFX-4.2
 
Michael,

Could you explain what you mean by modifying the journal file?

>By the way, I just got out your CFD Website,
>thank you for your contribution to CFX users.

I am glad you like it :)

David

Michael Song March 18, 1999 09:49

Re: Meshing with CFX-4.2
 
David, normally you should also get a journal file (*.db.jou) when using Build. This file can be edited manually. For example, you can change the center location and/or radius of a circular curve or even put a lot of pause lines in regenerating the model.

I like to keep journal files and modify them little bit as I need. Note that regenerating a model from a journal file is lot slower than the one reopened from a db file. However, the journal file is much smaller.

By the way, I tried to print out your thesis, but it seems to me it was set as readable-only. Can you change its setting? Thanks.

Michael



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