CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Open Source Meshers: Gmsh, Netgen, CGNS, ...

keeping/changing dimensions in imported meshes

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   September 24, 2009, 05:48
Default keeping/changing dimensions in imported meshes
  #1
New Member
 
bigred's Avatar
 
Matthew Philpott
Join Date: Aug 2009
Location: Belgium
Posts: 24
Rep Power: 8
bigred is on a distinguished road
I was just wondering, when I load an STL into netgen and then mesh it, export the mesh in neutral format and then import it into OF, is there a way to check or change the dimensions? At which step should it be done (STL formation, netgen import, meshing, netgen export or OF import)?

I know in blockMesh the dictionary contains a convertToMeters command to be able to set the mesh in mm or m etc. Is there a netgenNeutralToFoam dictionary with this option or is it a parameter you have to specify.

Thanks.
__________________
CAELinux 2009 + OF1.5
Ubuntu 9.04 x64 (jaunty jackalope) + OF1.6
bigred is offline   Reply With Quote

Old   September 27, 2009, 04:12
Default
  #2
Senior Member
 
Philippose Rajan
Join Date: Mar 2009
Location: Germany
Posts: 530
Rep Power: 16
philippose will become famous soon enough
Hi there,

A Good Morning to you!

When using STL geometry, Netgen does not make any automatic changes to the point co-ordinates, and the entire meshing is performed without any "unit awareness".... the co-ordinates are assumed to be dimensionless....

You can change the dimensions of your mesh (basically multiply all the co-ordinates by a conversion factor) after importing the mesh into OpenFOAM by using the utility: transformPoints

Internally OpenFOAM works with SI units... hence you should convert your mesh into "metre" (m).

For example, using the following command within the case folder converts a mesh whose co-ordinates are defined in "mm" to "m"...:

transformPoints -scale (0.001 0.001 0.001)

This command multiplies all co-ordinates by the factor "0.001".

Have a nice day!

Philippose
philippose is offline   Reply With Quote

Old   September 28, 2009, 03:38
Default
  #3
New Member
 
bigred's Avatar
 
Matthew Philpott
Join Date: Aug 2009
Location: Belgium
Posts: 24
Rep Power: 8
bigred is on a distinguished road
ok, thanks, I'll give it a try. So when checkMesh gives a report showing the complete volume as something like (0.1 -0.5 0) (0.5 0.5 3.0), then those units are in metres. A block that is 0.4m x 1m x 3m. But what I actually want is that the mesh is 0.4mm x 1mm x 3mm, then I should transformPoints - scale (0.001 0.001 0.001). Seems simple enough.
__________________
CAELinux 2009 + OF1.5
Ubuntu 9.04 x64 (jaunty jackalope) + OF1.6
bigred is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Getting prism to inflate into mixed tet-hex meshes Joe CFX 16 October 10, 2011 07:06
OpenFOAM compilation fails on applicationsutilitiesmesh geoffjay OpenFOAM Installation 12 April 29, 2008 15:26
OpenFOAM141dev linking error on IBM AIX 52 matthias OpenFOAM Installation 24 April 28, 2008 15:49
Using stitchmesh on imported gmsh meshes christian67 OpenFOAM Meshing Format & General Technical 0 November 26, 2005 05:22
Large 3D tetrahedral meshes Aldo Bonfiglioli Main CFD Forum 4 August 27, 1999 03:33


All times are GMT -4. The time now is 02:22.