forked from lijiext/lammps
58 lines
1.8 KiB
Plaintext
58 lines
1.8 KiB
Plaintext
"Higher level section"_Howto.html - "LAMMPS WWW Site"_lws - "LAMMPS
|
|
Documentation"_ld - "LAMMPS Commands"_lc :c
|
|
|
|
:link(lws,http://lammps.sandia.gov)
|
|
:link(ld,Manual.html)
|
|
:link(lc,Commands_all.html)
|
|
|
|
:line
|
|
|
|
Granular models :h3
|
|
|
|
Granular system are composed of spherical particles with a diameter,
|
|
as opposed to point particles. This means they have an angular
|
|
velocity and torque can be imparted to them to cause them to rotate.
|
|
|
|
To run a simulation of a granular model, you will want to use
|
|
the following commands:
|
|
|
|
"atom_style sphere"_atom_style.html
|
|
"fix nve/sphere"_fix_nve_sphere.html
|
|
"fix gravity"_fix_gravity.html :ul
|
|
|
|
This compute
|
|
|
|
"compute erotate/sphere"_compute_erotate_sphere.html :ul
|
|
|
|
calculates rotational kinetic energy which can be "output with
|
|
thermodynamic info"_Howto_output.html.
|
|
|
|
Use one of these 3 pair potentials, which compute forces and torques
|
|
between interacting pairs of particles:
|
|
|
|
"pair_style"_pair_style.html gran/history
|
|
"pair_style"_pair_style.html gran/no_history
|
|
"pair_style"_pair_style.html gran/hertzian :ul
|
|
|
|
These commands implement fix options specific to granular systems:
|
|
|
|
"fix freeze"_fix_freeze.html
|
|
"fix pour"_fix_pour.html
|
|
"fix viscous"_fix_viscous.html
|
|
"fix wall/gran"_fix_wall_gran.html :ul
|
|
|
|
The fix style {freeze} zeroes both the force and torque of frozen
|
|
atoms, and should be used for granular system instead of the fix style
|
|
{setforce}.
|
|
|
|
For computational efficiency, you can eliminate needless pairwise
|
|
computations between frozen atoms by using this command:
|
|
|
|
"neigh_modify"_neigh_modify.html exclude :ul
|
|
|
|
NOTE: By default, for 2d systems, granular particles are still modeled
|
|
as 3d spheres, not 2d discs (circles), meaning their moment of inertia
|
|
will be the same as in 3d. If you wish to model granular particles in
|
|
2d as 2d discs, see the note on this topic on the "Howto 2d"_Howto_2d.html
|
|
doc page, where 2d simulations are discussed.
|