2D disks in Couette flow

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1

Hello,

I am new to LAMMPS, but is there any way to use 2D disks in the Couette flow example (instead of spheres)?

https://github.com/CFDEMproject/LAMMPS/blob/master/examples/flow/in.flow.couette

This is because I would like to test the method of:

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.72.021309

Kind regards,

Andrew

2

Hello,

I am new to LAMMPS, but is there any way to use 2D disks in the Couette
flow example (instead of spheres)?

https://github.com/CFDEMproject/LAMMPS/blob/master/examples/flow/in.flow.
couette

​you are looking at the wrong github repository. please go to: ​

https://github.com/lammps/lammps/
the official LAMMPS homepage is at: lammps.sandia.gov

the CFDEMproject team maintains a fork of LAMMPS called LIGGGHTS with focus
on DEM and coupling to OpenFoam. it has over the years diverged quite a bit
from the upstream version and still uses a much older LAMMPS code base in
the non-DEM related parts.

This is because I would like to test the method of:

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.72.021309

​please check out the comments to the ​24 Mar 2017 patch at

http://lammps.sandia.gov/bug.html
and compare the online documentation at lammps.sandia.gov with your paper.
if it matches, you can do it, if not, you cannot.

​axel.​

3

Note that in the examples/flow/in.coutte script, the system is really

point particles, interacting via a LJ potential. So its not really spheres

or discs, just a 2d model.

What Axel referred to are granular models with frictional potentials,

which use fix nve/sphere, since the particles rotate. In Section_howto 6.2

it says:

NOTE: Some models in LAMMPS treat particles as finite-size spheres, as
opposed to point particles. See the “atom_style
sphere”_atom_style.html and “fix nve/sphere”_fix_nve_sphere.html
commands for details. By default, for 2d simulations, such particles
will still be modeled as 3d spheres, not 2d discs (circles), meaning
their moment of inertia will be that of a sphere. If you wish to
model them as 2d discs, see the “set density/disc”_set.html command
and the {disc} option for the “fix nve/sphere”_fix_nve_sphere.html,
“fix nvt/sphere”_fix_nvt_sphere.html, “fix
nph/sphere”_fix_nph_sphere.html, “fix npt/sphere”_fix_npt_sphere.html
commands.

That applies to granular models, but really any model with finite-size spheres

vs discs, b/c the only difference between them is the moment of

inertial for a sphere vs disc, which is used in the time integration

or the mass/density of the particle.

Steve