LIGGGHTS® - User Forum

Hey guys, I have done compression testing of particles in LIGGGHTS in 3D. Now, I want to do the same test in 2D. As per the documentation, I added command "dimensions 3" but I am getting an error while using "insert/rate/region" command and if I use "create_atoms" command by using the lattice for 2D, atoms are created, but the moment my wall touches the atoms, I get a message " Proc 0 Internal error", also in create atoms i am not able to add gravity. So, what is the correct procedure to model a simulation in 2D ?? and which visualization software is best to view it ??

Hi All,

I have a question related to the union of two region

In my simulation, I am currently defining a region as a sum of two adjacent cubes.
By looking at the .vtk of my simulation in paraview, I see that there is a small "empty space" (or gap) between the regions and I don't understand if

1) that comes from the division of the region (although it supposed to look like a single piece)
region regdown block 0.0 0.5 0.0 0.5 0.0 0.25 units box
region regup block 0.0 0.5 0.0 0.5 0.25 0.5 units box
region reg union 2 regdown regup units box

Hi All,

I have a problem/question about the servo wall

http://www.cfdem.com/media/DEM/docu/fix_mesh_surface_stress_servo.html

I want to first define two sub-regions, in which I want to insert two different particle distributions (pdd1 and pdd2 in the file).
After the distribution is complete, I want to insert a "servo - wall", from the top of the simulation box to compress both packings (pdd1 and pdd2)

Hey,

Dear All

I have a big problem with calculation time. I tried to simulated particles with 1 mm diameter but it takes too many times.

I think my problem is skin distance in neighbor command. How I can calculated optimized skin distance.

Regards
Esmaeil

Hello everyone,

For my thesis it was asked me to obtain the timestep of each simulation calculating it from the contact time (tc = pi / omega), for which I need stiffness and viscosity.

If I am using a pair style "hooke" and my inputs are Young, Poisson, Restitution , Friction and Characteristic Impact Velocity, is there a way to access the variables "k_n" and "gamma_n", when Liggghts has calculated it?

Thanks

Greetings,
Luca

Hi,

I am trying to extract information of contacts between particles from LIGGGHTS.

Contact Normal Forces, tangential forces, position, vectors, particle id contributing to each of the contact points.

Please give some idea how to do so from the software. Any information regarding these will be helpful.

Thanks in advance.

Dear all,

The stress/atom just calculate the pair stress between particles,not including the pair stress for the wall and particle. For my case, the pair stress between wall and particle is very important.

Is it possible for the developer to update this recently?

If not, how should I modify the pair.cpp, only the simple process is Ok.

Many thanks,

Leo

Hi everybody,

I am trying to "move" a primitive zplane along the x axis.

The command I am using is:
fix primZPLANE all wall/gran model hertz tangential history primitive type 2 zplane 0 shear x -0.05

When I leave out the part "shear x -0.05" I receive no error at all. As soon as I add it, the error I get is:
"ERROR: Expected floating point parameter in input script or data file (../fix_wall_gran.cpp:285)"

What am I doing wrong?

Best regards,
MiRa

Hi Everyone,

I am new to LIGGGHTS. In my simulations I have calculated some variables (they are averaged values) and I would like to dump them in the dump file.
Among the tutorials, forum and manual I mostly see that LIGGGHTS dumps information in one file per timestep (100 files = 100 tsteps), but i would like to have one big file with each line representing each timestep.

Does anyone have any suggestion or example?

Greetings
Luca