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Active Member
moldyflow
Posts: 8
Registered: ‎05-20-2010

3D meshing

692 Views, 6 Replies
07-22-2010 08:47 AM

Hello.

 

I have some questions about the options in the 3D "Generate Mesh".

 

Please explain;

 

1. Global edge length.

My default is set to 8.4 mm.

 

2. Maximum allowed edge length through thickness.

My default is set to 10.08 mm.

 

Thanks.

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Employee
franco.costa
Posts: 11
Registered: ‎07-25-2010

Re: 3D meshing

07-25-2010 05:15 PM in reply to: moldyflow

Hi,

Global Edge Length is used during the surface meshing stage.

Maximum edge length through the thickness is used as an additional meshing control to control the number of tetrhedral elements through the part thickness in any local area. There are two controls which govern this: The minimum number of elements layers and the maximum allowed edge length in the thickness direction. In each local cross-section, the tetrahedral mesh will be created which satisfies both of these constraints.

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Active Member
moldyflow
Posts: 8
Registered: ‎05-20-2010

Re: 3D meshing

07-26-2010 06:04 AM in reply to: moldyflow

Thanks, but can someone go more in detail? Like what is the global edge length doing to the mesh? How is it changing it? I got the layers part, but what does changing the parm do?

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Employee
franco.costa
Posts: 11
Registered: ‎07-25-2010

Re: 3D meshing

07-27-2010 09:41 PM in reply to: moldyflow

Sorry I wasn't clear,

the global edge length is used when meshing CAD surfaces, IGES surfaces, STL facets etc to get the initial/intermediate surface mesh before the 3D mesh is created. If you are launching 3D meshing when you already have a dual-domain surface mesh, then the global edge length parameter is not used

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Active Member
moldyflow
Posts: 8
Registered: ‎05-20-2010

Re: 3D meshing

07-27-2010 11:08 PM in reply to: moldyflow

Ok, I think its me that is not being clear. So if I want to mesh a part from scratch and my Global edge length is 18 mm. What does that mean? The total of all the edge for an element is 18 mm? And for Max edge though thickness, the way you describe it seems to be already set by the # of layers.

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Employee
franco.costa
Posts: 11
Registered: ‎07-25-2010

Re: 3D meshing

07-27-2010 11:53 PM in reply to: moldyflow

Global Edge Lengh relates to a single edge on a surface element (the distant between 2 nodes).

The "global" means it is a target value in an average sense. Some edge length will be more and some will be less, depending on the geometry etc).

 

Yes, the number of layers and the maximum edge length through the thickness do seem to control the same thing. Both conditions have to be satisfied. The reason for having two conditions is to ensure element quality and good solution resolution in both thin and thick cross-sections. In thin sections, the minimum number of layers will determine the element spacing, ensuring there are enough elements to capture temperature and shear rate variations through the thickness. In such regions the internal edge through in the thickness may be much less than the maximum allowed. In thick sections, maximum internal edge length will determine the spacing, stopping the element size getting too big. In such regions, the number of layers may be higher than the minimum requirement.

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Active Member
moldyflow
Posts: 8
Registered: ‎05-20-2010

Re: 3D meshing

07-28-2010 06:12 AM in reply to: moldyflow

Oh, I see. Your meaning of the "Max edge though thickness" makes sense and is very clear. Thanks for your help and patients. Take care.

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