Which compute styles, fix styles, and pair_styles are necessary or useful to simulate rotating geometries like Ball mills? I want to simulate a Ball mill with 2, 4, 6, and 8 lifter as well as with different radii (Attached Fig.). Any suggestion would be appreciated.
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 I want to simulate a Ball mill like this | 34.35 KB |
richti83 | Sun, 03/03/2013 - 17:46
A good starting point is the
A good starting point is the movingmesh tutorial in the examples/LIGGGHTS/ folder. If you have the geometry as STL file just change the filename, the simulation region (box) and the move/mesh command at the bottom of the script.
Mohammad Jahani | Tue, 03/05/2013 - 09:01
Can LIGGGHTS simulate a Ball Mill without STL files?
Thanks a lot richti83 for your useful comments. I am not familiar with STL files, can you please give me some information about them. Are they necessary for difining the geometry? Is there another way to difine the geometry except this? Finally, you mean only LIGGGHTS can simulate Ball Mills and LAMMPS cannot do this?
cstoltz | Tue, 03/05/2013 - 12:00
STL files are a simple way to
STL files are a simple way to define the geometry. See http://en.wikipedia.org/wiki/STL_(file_format)
You can define a couple of primitive objects within the LIGGGHTS framework, but for what you're describing, you will need to use an external package to generate the geometry and save it in an STL format.
LAMMPS cannot read STL files. This is a LIGGGHTS-only capability.
Regards,
Chris
Mohammad Jahani | Wed, 03/06/2013 - 09:23
External packages like what?
Thanks a lot Chris for your useful information about stl files. But I don't know what software is suitable and consistent with what I need? Can paraview generate the geometry I want and save the geometry in an stl format? Can AutoCad do this? What software you suggest?
cstoltz | Wed, 03/06/2013 - 12:02
Use a CAD package - AutoCAD,
Use a CAD package - AutoCAD, SolidEdge, SolidWorks, or any of a dozen others out there. You can usually save the geometry directly to an STL format, but be aware that the resulting file will usually contain many high aspect ratio triangular facets. If you want to get a cleaner mesh, save it out to IGS/STEP or similar and use gmsh to mesh it up better.
Chris
Mohammad Jahani | Thu, 03/07/2013 - 12:15
Can I use Linux-based CAD software like FreeCAD?
Thanks again dear Chris for your very helpful comments. Can I use Linux-based CAD packages like FreeCAD and Q-cad instead of Windows-based software like AutoCAD, SolidWorks etc.? Can you give me some information about IGS/STEP? Can I simply use gmsh software to define the geometry without using the above mentioned softwares?
cstoltz | Thu, 03/07/2013 - 13:37
You can use whatever CAD
You can use whatever CAD platform you like. The ones I listed were just examples.
IGS and STEP are both common easily exchanged file formats. Google either for more info.
You can do some basic CAD in gmsh, but you're probably better off using a more dedicated CAD package for anything complex.
Regards,
Chris
Mohammad Jahani | Sat, 03/09/2013 - 09:10
Is this procedure correct?
Dear Chris, Thanks a million! you mean after drawing the geometry in, for example, AutoCAD, I should save it out to IGS format instead of STL and use this IGS file as an gmsh input. Then save the gmsh output to a STL file. Then use this STL file in the LIGGGHTS input script file. Is this procedure correct or not?
cstoltz | Sun, 03/10/2013 - 03:57
That is one route. Another
That is one route. Another is to simply save from AutoCAD, etc., directly to an STL format assuming your CAD program will output that way. The caveat is that the STL file generated directly from the CAD program will likely have a lot of very high aspect ratio triangles, meaning that the geometry won't parallelize well. The gmsh generated one will likely not have the problem with aspect ratios, but will probably require a lot more facets.
Based on my (admittedly limited) experience, from a kinematic standpoint, I've found both options to provide similar results, with the direct CAD-generated STL files providing a little faster simulation than those using gmsh generated files. This will of course depend on how many facets each one in fact has, how well you can parallelize, and how much of the overall computational load depends on the geometry. From a stress calculation standpoint, I imagine the gmsh version is likely superior.
Regards,
Chris
Mohammad Jahani | Sun, 05/19/2013 - 14:13
The most commonly used software to generate 3d geometries?
I used Linux-based CAD platforms like FreeCAD and Q-cad, but in those softwares there is no possibility to save the geometry as STL format. Also in AutoCAD I could not generate a 3d geometry of the above-mentioned Ball Mill. Now, I want to know that "what is the most commonly used software to generate 3d geometries? Is that software support STL format?" Any suggestion would be appreciated.
richti83 | Sun, 05/19/2013 - 22:57
try step->stl conversion with gmsh
My workflow is:
1. draw the geometry with a CAD Tool you are familar with (scetch->extrude)
2. save the geometry as step (*.stp) file
3. load the step file into gmsh
4. mesh it in 2D (good results for simple meshes genereates (Option->Mesh->General) "MeshAdapt")
That's it.
Mohammad Jahani | Mon, 05/27/2013 - 13:59
I think SolidWorks is a better tool to draw the geometry
Dear richti83
Thanks a lot for your good information. The way suggested by you is good, but I have some problems with exporting the gmsh output to Paraview, where I cannot see 2D geometries.
Best Regards
Mohammad Jahani | Sun, 06/30/2013 - 12:09
Finally I meshed it up!
Dear richti83
Thanks again! I did these 4 stages and it worked. But I added 3 other stages!
5. Define-->3D ---> save (as *.msh)
6. load the msh file into gmsh
7. save the mesh as *.stl ---> load the stl file into paraview
Best Regards!
M.Jahani
AGl | Tue, 03/05/2013 - 14:05
GMSH STL
You can try to use GMSH - open-source meshing software, which is relatively simple to use and is available in many distributions "out of box".
Mohammad Jahani | Wed, 03/06/2013 - 09:14
Do you mean sudo apt-get install gmsh?
Thanks a lot AGI! I installed gmsh at ubuntu 11.10 using sudo apt-get install gmsh. Is it what you mean?