Creating complex geometries

Hi all,
I'm trying to simulate pouring of particles into various containers. By default, there are only two geometries available (cuboid and cylinder) in the fix wall/gran command. How do I create more complex geometries? Is there an open source software to create stl files which I can import using fix mesh/surface? This would then enable me to create complex geometries.

Thanks for the help.

Joel Martis

Forums:

LIGGGHTS® - User Forum

aaigner | Tue, 08/04/2015 - 23:27

Hi Joel,

some suggestions:

Gmsh
Salome

Gmsh is a simpler tool. If you have a nice CAD file, you can mesh it with gmsh.
Otherwise, you can use any CAD program to generate the geometry and then you can clean and mesh it with Salome.

To be honest, it is some work to generate a good mesh.

Bests
Andreas

Joel Martis | Wed, 08/05/2015 - 11:55

Thanks!

Thanks for the suggestions. I was wondering if there's a software where I can draw normally (like in AutoCAD) and export the model as a .stl without the need for another software.

Regards,
Joel

aaigner | Wed, 08/05/2015 - 15:01

Open-source volume based modelling

Well.. you can create models with Salome or a volume-based tool like FreeCAD. (or AutoCAD if you have a license) Salome can mesh the surface of such volume models.

But be aware of the fact that you normally don't need geometries including a wall thickness. That's the reason why we clean the data from the customer and mesh them then. So we remove wall-thickness, remove unnecessary parts (roundings and chamfers), .... to reduce the total number of triangles. Or create the geometry directly as a shell-based model.

One more point: Be careful! Standard CAD programs tend to export bad STL meshes, with coincident vortices/faces, very skewed triangles, ...

richti83 | Wed, 08/05/2015 - 15:44

best practice for me

I have had the same problem. Fortunately one can use the Autodesk Inventor license for research use for free. So I draw the model as surface geometry (no wall thickness, removing all unneded planes) and than export it as step file (bc. inventor can not export surface geometry as stl..)
Than I use netgen to mesh the step file to stl file. A good choice is max mesh-size=101 (mm) and min mesh-size is 100 (mm). this results in well parallelizable triangles with equal edge length. Of course the factor 100 depends on your geomitry size, you need to play a round with it ..