LIGGGHTS® - User Forum

Hi,

actually I tried to figure out in the LAMMPS manual, how I could access the kinetic energy of my granular system.
I understood, that LAMMPS is calculating the kinetic energy in a MD sence (ke = 1/2 Kb T).

I wonder if the ke in my thermo-output is calculated like 1/2mv^2 for all particles if I use the LIGGGHTS package?

Thanks in advance,

Sebastian

Hi,
I'm trying to use Kn and Kt instead Young Modulus. I wrote:

pair_style gran/hooke/history/stiffness 3 0
pair_coeff * *
...
fix m9 all property/global kn peratomtypepair 1 5000000
fix m10 all property/global kt peratomtypepair 1 5000000
fix m11 all property/global gamman peratomtypepair 1 0.7
fix m12 all property/global gammat peratomtypepair 1 0.7

But LIGGGHTS crashes without error message.
What I'm missing?

Thanks for any help

Andrea

Hello liggghts-team,

I want to simulate a role(cylinder) that moves linear along the systems X-Axis and it should rotate around its roll-axis.
Is there a way to do this?

1) I tried using 2 fix commands, but as expected only the late fix-command wins.
2) Rotate the role and moving the assembling linear around the role, is not a good alternative, producing wrong results.

Is it possible to script something like this:
even step = linear move
odd step = rotate role

hi, I'm new to this open source DEM code.
I try to find a User's Guide about LIGGGTS to get more information about the code. But it seems that there is only a install guide.

By the way, what's the requirement (or recommended) of computer hardware to use the code?

Thanks for help in advance.

Hi

I am trying to create a time-varying version of the "conveyor" feature of fix/mesh/gran. The most obvious way to do this is to update fix_mesh_gran.cpp every timestep. I have found the "time_depend" variable in fix_move_tri.cpp and other files. It seems to be a flag determining whether the function is time-dependent or not. Adding this to fix_mesh_gran does not seem to work - my programme is supposed to output to screen each timestep, but it doesn't. What else am I missing to make this work?

Hello,

may someone can give me a hint or help me with this.

I am asking for an alternative way to move one stl linear while another one is rotated,
because this does not seem to work:
fix movecad2 all move/mesh/gran linear 0.0 0.0 0.12 cad2 1
fix movecad1 all move/mesh/gran rotate 0.0 0.0 0.10 0.0 1.0 0.0 50. cad1 1

The szene is a rotating cylinder and a particle filled box is moved towards it.

Some ideas?

Thanks
rene

Hi All,

I need to get the list of contact forces for each atom. I am using LIGGGHTS as a library in my C++ code and need a class or function for getting that list. Do you have any comment?

Bests,
Ehsan.

Hi all,
I wonder if I can get the number of atom contacts on walls in LIGGGHTS? I'm using the fix mesh/gran/stressanalysis command to create boundary wall in simulation and I want to get the number of atom contacting with wall when wall moves. What's more, I also want to get the position of the geometrical centre of the wall after moving.

Can anyone help me with that?

Cheers,
Tao

Hello everybody,

Because of high simulation effort I'd like to simulate particles in a container in 2d.
I already simulated a small model in 3d where the ouput of forces exerting on container walls works perfectly fine with the fix cad mesh/gran/stressanalysis.

- Now I have problems with outputing forces in 2d (fix mesh/gran/stressanalysis works just with meshes on 3d-CAD, right?)
- So, instead of importing a CAD in 3d, I use the fix wall/gran/history command to import walls in my 2d simulation. How is it possible to output forces on these walls?

Thanks very much in advance,

Hi.
I have a problem with per-atom stress calculation.
I modify examples/packing script in order to calculate and dump per-atom stresses. So, I add the line:

64: compute st all stress/atom ke pair

and modify the dump command:

68: dump dmp all custom 350 post/dump.packing id type type x y z ix iy iz vx vy vz fx fy fz omegax omegay omegaz radius c_st[1] c_st[2] c_st[3] c_st[4] c_st[5] c_st[6]

But I got a error:

ERROR: Per-atom virial was not tallied on needed timestep

What is this?
I attach modified script

======
Upd: The script