LIGGGHTS® - User Forum

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.

Hi all,
I'm new to LIGGGHTS, and know quite little about the code. Thus, this question may appear to be quite simple for all of you.
In the simulation code, we just use numbers, e.g. 1,2... to represent different types of atom. I just wonder what's the really meaning of atom_types? Is there any relationship between these numbers and real atom_types?

Please give me some ideas about that.

Cheers,
Tao

Hello all !

I tried to define a variable function for youngs modulus , poisson ratio and the 2 coefficients as temperature dependent, but encountered an error telling me the values must be floating point.

Is there any way of defining the materials properties in liggghts as dependent on temperature or timestep for example ?

If so, what's the easiest way of doing so ? (I assume it involves the modification of some code)

Thanks !

Hi Liggghts users,
I'm new to LIGGGHTS. Recently, I tried to import CAD mesh file (stl file) into my model, but resulted in errors.
It always says:
Importing STL file 'simple_chute.stl'
ERROR on proc 0: Cannot open stl file simple_chute.stl

Actually, I put both LIGGGHTS in file and stl file in the same folder. But the same error occurs every time I run the simulation. I do not know what's going on. Can anyone help me about this?
Many thanks!

Yours,
Tao