LIGGGHTS® - User Forum

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

Hi all,
Can we define functions in LIGGGHTS script? I mean, define a section of codes that can be used elsewhere in LIGGGHTS script.

Thanks in advance.

Cheers,
Tao

Hi,

I may modify the LIGGGHTS code for a new contact model and do some basic benchmark tests. May anybody tell me how to fix the position and rotation of a particle in a simulation (its force and interaction with other particles remained ), and how to output the damping force of a particle?

Regards
Jerry

Hi,
I'd like to see particles as a kind of "grid" (see the picture I attached).
Do I have to set some group to make this?

Thanks for any help

Andrea

Hey Chris,

There has been a recent paper published in Powder Technology: An investigation of the comparative behaviour of alternative contact force models during elastic collisions (2011) C Thornton, S J Cummins, P W Cleary; which may be of interest for you.