LIGGGHTS® - User Forum

I've used a DEM software, i try to learn the "liggghts", but I 'm still confused about the key word "seed" in fix command , which could not be found a corresponding value or definition in the DEM software. So is there a clear definition or meaning about this key word? Hope helps from you!

Hello
I am doing wall friction test simulation. The procedure is as follow
1. Fill a cylinder with particle
2. Add a constant force of 100 N and move the cylinder against wall with constant velocity
3. While cylinder is moving against the wall the force is constant
4 I want a graph between normal force and shear force on the wall

Can any body help me in this?

Hi all,
I want to create two particles with two different id using the following command
create_atoms 1 single 0.95 0.4 0.5
set atom 1 type 1 diameter 0.02 density 2500 vx 2 vy 0 vz 0
create_atoms 2 single 0.99 0.4 0.5
set atom 1 type 2 diameter 0.02 density 2500 vx 0 vy 0 vz 0

but when I trying to compile the script file it says
ERROR: Invalid atom type in create_atoms command (../create_atoms.cpp:102)

Can anyone please enlighten me that waht I am doing wrong?

Thanks and regards,
Sourav

Hello
I am doing compression test simulation and I have the initial position of the particle. I want to read the particle data from file and give it to liggghts for further DEM simulation.
1. how can I read it. (command for it)
2. what is the file format that liggghts accepts.

I have been using fix insert/stream to add particles into a simulation through an insertion face. However, the specified particle rate is not obtained if I set a high value of particle rate and a low value for the inflow velocity. I presume the absolute limit of this would be when the spheres are tightly packed, but when I visualise the inlet box using the correct particle size in paraview (glyph), the particles are well spaced out. Can anyone explain what is happening and what is the limiting criteria for correct particle rates to be achieved?

Many thanks!

I'm trying to initialize a simulation with a particle size distribution, created using particledistribution/discrete -> insert/pack, then grown using adapt to increase the volume fraction to 40%. If I try to run the simulation multithreaded, I get MPI faults, and when I run it single threaded I get a segmentation fault. Previously, when using a single particle size, I used the 'scale no' option and had no problems. Has anyone else had trouble with fix adapt 'scale yes'?

I´m new user of LIGGGHTS, I´m working on a simulation that consist in a drum with a little hole at the bottom, and inside the drum a impeller. My goal is see the mixture of material, and the material at the outlet. Nevertheless, the trouble that I have right now is when I import the mesh for the drum and for the impeller I can´t have the impeller inside the drum. I review the documentation, but i don´t have a clear answer.
I attach part of the code i made. I hope someone could help to solve the trouble.
Regards,
CR

Dear all,

Do you know how to obtain the particle collision frequency/number?
maybe in dump command?

Thank you!

Hanqiao

I am running a test simulation (see attached input file) to check energy conservation in liggghts for the case where there is no damping or sliding and only the elastic springs in the normal and tangential direction are active. The damping is set to zero for both normal and tangential contact and the coefficient of friction is set very high to prevent energy loss by sliding. Thus I expect the total energy to remain pretty much constant over time. However the total energy at the end of the simulation is much lower than at the beginning.

Hello,
I am attempting to use the servo command to place a "constant" force onto a bed of particles in the z direction.

I am using the following commands to do so