[Netgen] Netgen mesh settings for STL geometries

lucchini · August 16, 2007, 06:56

Hi all,

I started using netgen a couple of weeks ago and I found it a very powerful tool considering the high mesh quality it is able to provide for complex geometries.

I wonder if someone in this forum knows the meaning of the following settings in the Meshing Options - Mesh size window:

1) Elements per curvature radius
2) Elements per edge
3) STL - chart distance
4) STL - line length
5) STL/IGES/STEP - close edges
6) STL - surface curvature
7) STL - edge angle
8) STL - surface mesh curv

Any kind of help is very appreciated.

Thanks in advance

Tommaso

philippose · August 16, 2007, 15:26

Hello Tommaso,

A good day to you!

I have been using Netgen for over a year now, and I personally find it to be the best opensource mesher available, by a far call :-)! Nothing comes close to the robustness, ease of use, and bug-free operation of the program!!

However, as you have found out, documentation is not really the strong point of the program :-)! I have tried to contact Joachim Schoeberl with exactly the questions you have posted, but have not got a reply yet (and that was almost a year ago :-)!)

Anyway... off-late, I have started scouring the source-code of Netgen, first, to understand what each of those parameters mean, and then, to understand how it works, so that I can tweak it up.

For example, my idea is to try and implement a modified "Ruppert-Shewchuk" algorithm which I found in a paper, which overcomes one of the biggest problems of Netgen... its in-ability to control the mesh length scale at places where there are surfaces close to each other in a satisfactory manner.... it always ends up with just one layer of cells between the two surfaces, which ofcourse, is not good for CFD.

Now... so far I have only documented the functioning of the parameters in my head, but I think the time has come to try to make a document which explains the things I have (hopefully) understood. I hate documentation though!!

How quickly do you need answers to your query? Would it be ok, if I try to come up with a PDF, instead of trying to explain things here? It will take some time though :-)! I started typing it out here on the forum, but then cut-pasted it into a "tex" file.

Have a nice day!

Philippose

lucchini · August 16, 2007, 15:46

Hi Philippose,

thanks for your kind reply. A pdf file about netgen would be really helpful for lots of users. Take your time to do it, there is no hurry.

Thanks again,

bye

Tommaso

vikramanvikraman · March 7, 2011, 02:02

dear mr Philippose Rajan

i am vikraman i am trying to generate a volume mesh from an stl file
with netgen, initially it did once but it started crashing when completing about 99% of generation saying run time error i hav upgraded windows from 32 bit to 64 bit and have amd phenom quad core with 8gb ddr3 ram machine i have tried all my best even sent mail to joachim no any reply from him
can you pls help and suggest how to over come the problem
thk u

August 16, 2007, 06:56	Netgen mesh settings for STL geometries	#1
lucchini Member Tommaso Lucchini Join Date: Mar 2009 Posts: 87 Rep Power: 17	Hi all, I started using netgen a couple of weeks ago and I found it a very powerful tool considering the high mesh quality it is able to provide for complex geometries. I wonder if someone in this forum knows the meaning of the following settings in the Meshing Options - Mesh size window: 1) Elements per curvature radius 2) Elements per edge 3) STL - chart distance 4) STL - line length 5) STL/IGES/STEP - close edges 6) STL - surface curvature 7) STL - edge angle 8) STL - surface mesh curv Any kind of help is very appreciated. Thanks in advance Tommaso

August 16, 2007, 15:26	Hello Tommaso, A good day t	#2
philippose Senior Member Philippose Rajan Join Date: Mar 2009 Location: Germany Posts: 552 Rep Power: 25	Hello Tommaso, A good day to you! I have been using Netgen for over a year now, and I personally find it to be the best opensource mesher available, by a far call :-)! Nothing comes close to the robustness, ease of use, and bug-free operation of the program!! However, as you have found out, documentation is not really the strong point of the program :-)! I have tried to contact Joachim Schoeberl with exactly the questions you have posted, but have not got a reply yet (and that was almost a year ago :-)!) Anyway... off-late, I have started scouring the source-code of Netgen, first, to understand what each of those parameters mean, and then, to understand how it works, so that I can tweak it up. For example, my idea is to try and implement a modified "Ruppert-Shewchuk" algorithm which I found in a paper, which overcomes one of the biggest problems of Netgen... its in-ability to control the mesh length scale at places where there are surfaces close to each other in a satisfactory manner.... it always ends up with just one layer of cells between the two surfaces, which ofcourse, is not good for CFD. Now... so far I have only documented the functioning of the parameters in my head, but I think the time has come to try to make a document which explains the things I have (hopefully) understood. I hate documentation though!! How quickly do you need answers to your query? Would it be ok, if I try to come up with a PDF, instead of trying to explain things here? It will take some time though :-)! I started typing it out here on the forum, but then cut-pasted it into a "tex" file. Have a nice day! Philippose

August 16, 2007, 15:46	Hi Philippose, thanks for y	#3
lucchini Member Tommaso Lucchini Join Date: Mar 2009 Posts: 87 Rep Power: 17	Hi Philippose, thanks for your kind reply. A pdf file about netgen would be really helpful for lots of users. Take your time to do it, there is no hurry. Thanks again, bye Tommaso

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March 7, 2011, 02:02		#4
vikramanvikraman New Member vikraman Join Date: Mar 2011 Posts: 2 Rep Power: 0	dear mr Philippose Rajan i am vikraman i am trying to generate a volume mesh from an stl file with netgen, initially it did once but it started crashing when completing about 99% of generation saying run time error i hav upgraded windows from 32 bit to 64 bit and have amd phenom quad core with 8gb ddr3 ram machine i have tried all my best even sent mail to joachim no any reply from him can you pls help and suggest how to over come the problem thk u