LIGGGHTS® - User Forum

Hello Team,

Greetings. I hope, you are all doing good. I'm working on homogeneous simple shear simulation using the following two methods.

I'm trying to use rRESPA with a fix, however without the fix_modify respa options in lammps I'm unsure how to set the loop to apply fix forces at. Does anyone have any experience with this in LIGGGHTS? I see many fixes, such as fix_efield have rRESPA infrastructure in their code.

Thanks,
Thomas Leps

Hello everyone, I want to obtain a densest sample with equal sized spheres. I am using radius expansion method，and there is a factor named alpha target，referring to the packing density after expansion(I guess)，and I want to know the maximum value of this factor that can be used,thanks.
Best regards.
Zhao

hello everyone i hope ur all doing well i am a new ligggths user i need help i want to add an electrostatic field to attract granuls or push them if possible with positive and negative voltage to make a granular separation i am trying to modify the chute wear scrit by adding efield command but it's not working getting the following error thank you all

atom_style hybrid charge granular
atom_modify map array
boundary f f f
newton off

communicate single vel yes

units si

Hello!

I've been running a simulation with timestep 2.5e-7 and there were no warning messages. Once my computer shut down so I had to restart the simulation and used read_dump command with 'add' set to 'yes' for this. After I have restarted it, there were following messages:

WARNING: time-step is 397.197160 % of rayleigh time (../fix_check_timestep_gran.cpp:200)
WARNING: time-step is 63.994760 % of hertz time (../fix_check_timestep_gran.cpp:208)

Hi everyone,

I am trying to compute the torque on all the meshes of a given stl. In LIGGGHTS, I got the following module:
mesh module stress

I used it in script in the following way:
fix st all mesh/surface/stress file Frustum-1.stl type 1 wear

But I am unable to get the required output. I tried outputting it using thermo_style custom. But what I obtain is a series of just 9 zeros coming in rows. The values cannot be 0 actually. Moreover, it does not give the meshwise values.

Hi all,

I am encountering a problem here where my particles are disappearing and not behaving normally.
I am simulating a closed-end cone that filled with 100 micrometer diameter particles.
I notice that when I bigger diameter particle (smallest I can do is 150 micrometer diameter), the simulation still works and doesn't behave strange. So the problem only occurs on diameter less than 150 micrometer.
Is there anybody that can help me with this?

I also attach the .avi file but can only upload it in .txt, you can change the extension.

Hello everyone.

What is the best way to start learning liggghts as there are a lot of commands in the input script, so can you give some tips as to how to begin learning?

Hello everyone,

I am wondering why my simulation is showing spheres that are "floating". Does this happen due to the property of materials? In the screen shot, particles floating in "air" for multiple time steps and not moving much after particle collision. It didn't happen with my other practice scripts.

I have attached my script, could someone critique it please? This is my first time really exploring liggghts so my script is messy and I would really appreciate someone pointing out errors and tips.

I have attached a screenshot of what paraview is showing.