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Derek March 23, 2007 09:37

Long pipe
 
Hi,

I want to do meshing on a long pipe with small holes on the wall. As the hold is small comparing to the pipe length, I cannot complete meshing because the mesh size was too small. Could anyone tell me how to solve this problem? Thanks

I am using ANSYS CFX WORKBENCH 10.0.

thanks, Derek

Joe March 23, 2007 09:42

Re: Long pipe
 
Unstructured: Create multiple mesh domains with widely differing mesh sizes.

Structured: Relatively simple depending on the details of the hole spacing.

Derek March 23, 2007 09:49

Re: Long pipe
 
Hi Joe,

If mesh size depends on the hole. The mesh quantity will be too many and the computer is unable to run for it.

Do you have other advise?

Glenn Horrocks March 25, 2007 18:26

Re: Long pipe
 
Hi,

Break the pipe up into segments. Use a swept mesh in the long bits and stretch the grid out, and use an unstructured mesh at the intersections and other 3D features.

Glenn Horrocks

G March 26, 2007 09:04

Re: Long pipe
 
Hi,

Glenn gave you one advice, but I think you should just try to prescribe very dense mesh at the holes compared to the mesh elsewhere (the body mesh doesn't have to be so dense, just decrease the mesh size at the hole surface drasticly).

If that doesn't work try what the guys suggested.

Derek March 27, 2007 07:42

Re: Long pipe
 
Hi Glenn,

After break the pipe into segments, could you tell me how to link them up and back to one long pipe.

thanks


Derek March 27, 2007 07:44

Re: Long pipe
 
Hi,

I dont' know how to set different mesh size for the pipe. Would you give me a hand....

G March 27, 2007 08:09

Re: Long pipe
 
Hi,

I am using ICEM CFD for meshing, but I know that it can be also done in CFX Workbench. You should prescribe certain mesh control at chosen location (it can be a point, curve or a surface).

I hope someone could give you a specific direction how to do it in Workbench or check some tutorials.

Glenn Horrocks March 27, 2007 19:02

Re: Long pipe
 
Hi,

In workbench slice the bodies up and make multi-body parts out of them. Look up multi body parts in the documentation for workbench.

Glenn Horrocks

Derek March 31, 2007 01:20

Re: Long pipe
 
Hi G,

You said I can specify the point, curve or surface. But actually the problem would be volume mesh, is it? There are too many triangle needed if I set the mesh size based on the tiny holes on the pipe.

Do you have any idea for it, thanks.

G April 2, 2007 05:52

Re: Long pipe
 
Hi!

You can set a global element size, which should be rather big and you can also set a surface mesh parameters (decrease mesh size on the holes). The volume mesh will be created based on both parameters (global and specific surface parameters).


Glenn Horrocks April 2, 2007 18:18

Re: Long pipe
 
Hi,

That's why, if possible, you should break the model up into sweep mesh sections for the long thin sections without branches and only use tet meshes in the junctions. The sweep meshes allow you to use element aspect ratioes much higher than tet meshes so you get a quality mesh with far less elements.

Not all geometry can be broken down into swept bodies but if it can it is a big advantage.

Glenn Horrocks


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