LIGGGHTS® - User Forum

Hi

I am trying to apply forces on atoms based on one of their coordinate positions. I have implemented this type of force successfully on a single atom using

run 50000 every 10 "fix acforce all addforce ${Force} NULL NULL region ac"

where

variable Force equal (variable function(v_xposition))

I have introduced additional atoms into the system using

read_data grann

in which I specify their positions, initial velocities, etc

To my understanding I require

Hi

I'd like to set up a simulation for a dense suspension (volfrac: 0.6). To reduce the complexity of the model I'm trying to include the fluid phase with "pair_style lubricate". This pair style is part of the colloid package. And it seems to me, that this package was not installed when I installed LIGGGHTS. Playing around to with the atom_style command I found out that the following atom_styles are missing:
- colloid
- dipole
- ellipsoid
- peri
and my guess is that these packages are not installed.

HI!

I wanted to change the angle of the chute in the after 8000 runs. Therefore I did the following
....
#the chute
fix cad3 all mesh/gran chute.stl 6 1.0 0. 0. 0. 0. 48.3 0.
fix movecad all move/mesh/gran rotate 0. 0. 0. 0. 0. 1. 7.0 cad3
......
fix granwalls all wall/gran/hertz/history 3 0 mesh/gran 5 cad1 cad2 cad3 cad4 cad5
......
fix ins1 nve_group pour/dev mass 3.888 10001 distributiontemplate pdd2 region bc massflowrate 0.5554 vol 0.6 20
......
run 8000 upto
unfix ins1

unfix cad3
unfix movecad
fix cad3_l1 all mesh/gran chute.stl 6 1.0 0. 0. 0. 0. 52.5 0.

Hi everyone,

Are there any commands to see how many particles are in contact with a wall? Or in the code, which part can give a output for the number of particles on a wall? I see the fix mesh/gran command. It can only output the force and torque.

Thanks a lot.

J.Wang

Dear LIGGGHTS users,

Hello,

I am trying to model flow of grains through a slit under confining pressure (imagine sand grains in a fracture confined under a certain pressure). The way I'm doing this is by creating two rigid walls made of atoms arranged in a lattice with a force applied to each atom. However, once I create the lattice and apply the rigid command, all atoms in the lattice are returned with NaN or -NaN in the dump files after the first step. Code is attached.

I know I'm just missing a simple step. Ideas?

Thanks,

Roman

I am trying to run a simulation where particles are poured into a thin, tall container. I had the idea to begin pouring (with insert/rate/region) near the bottom, and move the insertion region vertically as the pile of grains grows. This is so that they won't have to fall all the way from the top of the box to the bottom.

However, when I try to run a simulation like this, it stops after a few insertions. By "stops", I mean it seems to get caught in an infinite loop somewhere. If I pour from a non-moving region, this problem doesn't arise.

Dear users,

last week I posted about problems with my ball mill simulation. The problem was that the balls adhered underneath the lifting bar of the stl geometry. I was told to improve the mesh because of high skewness and aspect ratio.

After I've done it, the problem still remains! The balls still adhere to the bar!

I will attach the new mesh, so you can check it.

Please tell me what the real problem is and what do I have to do to solve it.

Thank you!

Kind regards,

Eugen

Dear all,
I could not find any info on how to record to dump file
moving walls defined with:
fix myoscillatingwall all wall/gran/hertz/history 3 0 zplane 0.0 NULL 1 wiggle z 0.001 0.02
I had supposed that since I only need a simple movement
like this I could skip building a mesh, but how can I
export the wall position (to read it in paraview)?
Note that the wall works as intended, the particles
correctly interact with it.
Thank you,
Alessandro

Velocity Verlet integration assumes that acceleration only depends on position , and does not depend on velocity. Then is it logical to perform Velocity Verlet integration on granular where there is velocity dependent terms in formula of force and consequently acceleration depends on the velocity?

Thanks