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Re: Improved netgen 1-2-3D mesh + “limit size by curvature"

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Re: Improved netgen 1-2-3D mesh + “limit size by curvature"

Posted by mihe at September 11. 2020

Hi,
About the netgen 1-2-3D mesh with the option “limit size by curvature”. The god thing with this option is that you with very lite specification can create a mesh that often fulfill your needs for stress evaluation. Hence you can set the mesh density you need at all transition fillets. However, one annoying thing is that, Salome detects small edges and even gaps between surfaces and also refines the mesh in these areas.

See attached examples. I have created 2 boxes 200x200x200mm and one cylinder with radius 50mm and length 200mm. Between the cylinder and one of the boxes I have a 10mm fillet. Between the two boxes there is a gap of 1mm. I decide I want ~3 elements through the fillet and calculate the mesh. See attached pictures and model file. In the other example there is a step instead of a gap.

I think you get the point. At the transition fillet it works great. But a lot of elements are  wasted at the gap/step between the two boxes.

In my opinion you seldom want to refine the mesh at a corner/edge. An improvement would be if the option "Nb. segs per radius" could be defined without specifying "Nb segs per edge".

-Would you consider to change this?

-Or can this behavior already be avoided in some way? -How?

BR/Micke

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Re: Improved netgen 1-2-3D mesh + “limit size by curvature"

Posted by mihe at September 11. 2020

Next picture/Micke

 

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Re: Improved netgen 1-2-3D mesh + “limit size by curvature"

Posted by mihe at September 11. 2020

Next picture/Micke

 

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Re: Improved netgen 1-2-3D mesh + “limit size by curvature"

Posted by Saint Michael at September 12. 2020

Hi Micke

You can avoid refinement at the gap by defining a sub-mesh on one of the boxes. 

St.Michael

Re: Improved netgen 1-2-3D mesh + “limit size by curvature"

Posted by mihe at September 22. 2020

Thank you. Ok that solves part of the issue.

-But do you not agree that it would be quite a big improvement  if the option "Nb. segs per radius" could be defined without specifying "Nb segs per edge"?

For FEA stress analysis "Nb segs per edge" usually menas  that more dof:s that necessary are spent where you do not want them.

BR/Micke

 

 

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