[Discussion] Resources!

[ZoeRichter]

This issue simply contains links to some resources I've mentioned in the past, collected here so you can find them. Feel free to add comments here adding more if you find something else to add - but also remember to use the Zotero to hold papers you want to reference in your report(s).

• First off, the LAMMPS website and manual. You've already got past the installation process, so the Command Reference section is probably what you'll use most often.
  • the fix section is where you will find the fixes for adding heat, gravity, or pouring
  • The pair style granular is what you'll want to use to simulate particle physics.
    • You will want to reference the 3 papers this page cites - they are already in the group Zotero
    • This pour requires using the atom_style sphere. If you want to be able to add heat, you may need to use a hybrid style that combines the sphere style with whatever atom_style you need to track heat in the particles.
  • I've found these granular movies from the LAMMPS movie gallery have been super helpful to me, and the box example specifically should be useful when you want to rotate a cask. If you're trying to learn LAMMPS, I'd recommend going through the input file for these (or at least for the box example) and looking up what the different commands in the input file do. If you want to see an example of pouring particles, the funnel example is straightforward.

Some general LAMMPS tips/advice:

• Your time step is going to be on the scale of microseconds - possibly even a tenth of a microsecond. Your time step size is scaled based on the anticipated collision time, and trying to significantly increase your dt to speed things along will only result in inaccurate physics.
• The first time you load pebbles into any given container, I would recommend giving the simulation time to just run under the influence of gravity to let everything settle/come to rest. This will probably take much longer than you expect - I'd give it a few 100K timesteps at least, to start with. Save those settled pebble coordinates (you can have LAMMPS make a dump file of them), and then use those as a basis for future simulations - pouring in sand, shaking, tipping the container, etc. Saving the settled coordinates means you don't have to do this all the time. If you use Ghastly to fill a container, it should be settled by the time it finishes, but it's always best to double-check.
• These simulations will take a long time. Days, maybe even over a week. You will need to plan ahead, and start running early so you don't run out of time. Sometimes it's not clear that there's an issue until partway into a simulation, so you should also check in on how it's going (this is part of why I have my simulations create a gif using the dump image command)

[ZoeRichter]

For importing a triangle-based STL mesh, you'll want to use the create_atoms mesh command. Here is the forum post I found that discusses this.