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Re: Problem with internal edges/wire in a 2D Mesh

Posted by Ype Attema at July 04. 2018

I want to make a 2D Mesh that includes internal edges which should be followed by the mesh elements. I managed to get this to work by using “geompy.MakePartition” and include the internal edges in the face to form one entity that can be made into a mesh.

However, when making the mesh I noticed that including these internal edges in the face causes the computing time to increase significantly.In my attached script the mesh without internal edges takes about 5 seconds to compute (Grid_Mesh_1), while the grid with internal edges takes 2 minutes (Grid_Mesh_2). The computation reaches 99% quite quickly, but after that it takes a lot of time. When these internal edges cross the face boundaries (cutting the face in two) then the computing time is normal again, 5 seconds only.

Futhermore, I noticed that 12 nodes on the Mesh boundary have an object id value of 1 (corresponding to an internal mesh node) when exporting the mesh to a GMF file (.mesh). This is exactly the same amount of nodes in the internal edges (which do have an object id value for a node on the model boundary). This seems rather odd to me.

 

Is there a better way of forcing the mesh elements to follow certain internal edges in a face (edges which do not cut the face in two)? Or is there another way of improving the computing time for this case? (Or perhaps this is just a difficult constrained for the grid generator?)

I tried this in salome version 8.3.0 on windows and on 8.4.0 on linux (virtual box).

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Re: Problem with internal edges/wire in a 2D Mesh

Posted by Saint Michael at July 04. 2018

Hi

There is no a better and faster way to do it. I suppose a commercial mesher (MG-CADSur) is faster.

St.Michael

Re: Problem with internal edges/wire in a 2D Mesh

Posted by Ype Attema at August 30. 2018

Hi St.Michael,

Thanks for your reply.

However i still find it strange that the NETGEN 1D-2D algorithm is stuck at 99% progress for a long time when meshing Grid_Mesh_2. 

Certainly considering that meshing Grid_Mesh_1 only takes a few seconds, while the only difference between the two geometries is the inclusion of a internal wire by means of a “geompy.MakePartition” (see red line in figure).

Do you have any idea why there is such a difference in meshing time?

And why NETGEN 1D-2D algorithm hangs up on 99% progress?

Thanks in advance.

Regards,
Ype Attema

 

 

 

 

 

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Re: Problem with internal edges/wire in a 2D Mesh

Posted by Saint Michael at August 30. 2018

It is really very strange. No idea why. After 99% NETGEN does optimization and conversion to quadratic. If you switch off these parameters, meshing is fast.

St.Michael

Re: Problem with internal edges/wire in a 2D Mesh

Posted by Ype Attema at August 30. 2018

Hi St.Michael,

Thanks again for your fast reply.

How can I switch off conversion to quadratic?

Thanks in advance.

Regards,
Ype Attema

 

Re: Problem with internal edges/wire in a 2D Mesh

Posted by Saint Michael at August 30. 2018

In your script you define generation of quadratic elements:

NETGEN_2D_Parameters_1.SetSecondOrder( 1 )

To switch it off

NETGEN_2D_Parameters_1.SetSecondOrder( 0 )

St.Michael

Re: Problem with internal edges/wire in a 2D Mesh

Posted by Ype Attema at September 03. 2018

Hi St.Michael,

Thanks for your reply, switching off  optimization and conversion to quadratic indeed speeds up the meshing process a lot. However for the quality of the mesh the optimization is needed in my opinion.

Perhaps the optimization can be speeded up if the optimization stop criteria can be lowered, while the end result is still a good quality mesh. I found that the optimizer options can be adjusted in the NETGEN software, is it also possible to adjust the optimizer options in SALOME script?

Regards,

Ype Attema 

 

 

Re: Problem with internal edges/wire in a 2D Mesh

Posted by Saint Michael at September 03. 2018

Hi Ype Attema

What is the name of "optimizer options" in NETGEN. Do  they present in NETGEN GUI?

St.Michael

 

Re: Problem with internal edges/wire in a 2D Mesh

Posted by Ype Attema at September 03. 2018
Hi St.Michael,
 
See figure attached.
 
 
Regards,
 
Ype Attema
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Re: Problem with internal edges/wire in a 2D Mesh

Posted by Saint Michael at September 03. 2018

SALOME does not provide access to these options :(

St.Michael

 

Re: Problem with internal edges/wire in a 2D Mesh

Posted by Ype Attema at September 03. 2018
Hi St.Michael,
 
Too bad.
 
Thanks for the great help!
 
Regards,
Ype Attema
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Activate by Ype Attema on Jul 04, 2018 01:11 PM
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