netgen - Bad geometry for volume mesh generation?

thommycorner · January 10, 2013, 06:21

Good morning everybody,
this is my first post and since I am rather a coder than an engineer I am pretty new to the domain of CAD data, so I hope that I do not ask too obvious questions.

Right now I am trying to automate a mesh generation process with netgen, but I have some example files that do not seem to work for me.
I keep getting a surface mesh, but no volume mesh is generated, so I suspect that the geometry that I am using is corrupt or in any way incorrect.

Could anybody please have a look at the attached iges or step file and maybe give me a hint on what the problem might be?

Any help would be greatly appreciated!
Best, thommy

philippose · January 10, 2013, 07:44

Hello Thommy,

A Good Day to you!

I just had a look at your files, and the problem is, that the geometry has been exported from the CAD software in the form of "shells" rather than a "solid".

What you need to do is:

1. Go to the Geometry -> IGES/STEP Topology Explorer/Doctor
2. Click on "Analyze Geometry"
3. Uncheck all the ticks present except for the one for "make solids"
4. Click on "Heal Geometry"

Once this is done, you can mesh the geometry, and Netgen will also create the volume mesh for you.

The easier approach is to probably export the geometry from the CAD Software directly as a solid rather than as shells.

Hope this helps!

Have a nice day!

Philippose

thommycorner · January 10, 2013, 08:37

Hi Philippose,

thank you for your quick and helpful reply. I suspected something like that and will try new example files.

I found your suggestion to use the step/iges doctor in another thread, but in my netgen installation (5.0 on win) the iges/step doctor seems to be disappeared. Maybe I'm missing some environment variables.

Thanks a lot for your help and a great day for you, too!
Cheers,
Thommy

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January 10, 2013, 07:44		#2
philippose Senior Member Philippose Rajan Join Date: Mar 2009 Location: Germany Posts: 552 Rep Power: 25	Hello Thommy, A Good Day to you! I just had a look at your files, and the problem is, that the geometry has been exported from the CAD software in the form of "shells" rather than a "solid". What you need to do is: 1. Go to the Geometry -> IGES/STEP Topology Explorer/Doctor 2. Click on "Analyze Geometry" 3. Uncheck all the ticks present except for the one for "make solids" 4. Click on "Heal Geometry" Once this is done, you can mesh the geometry, and Netgen will also create the volume mesh for you. The easier approach is to probably export the geometry from the CAD Software directly as a solid rather than as shells. Hope this helps! Have a nice day! Philippose

January 10, 2013, 08:37		#3
thommycorner New Member Thommy Corner Join Date: Jan 2013 Posts: 3 Rep Power: 13	Hi Philippose, thank you for your quick and helpful reply. I suspected something like that and will try new example files. I found your suggestion to use the step/iges doctor in another thread, but in my netgen installation (5.0 on win) the iges/step doctor seems to be disappeared. Maybe I'm missing some environment variables. Thanks a lot for your help and a great day for you, too! Cheers, Thommy