LIGGGHTS® - User Forum

Does anyone know how per multisphere quantities can be manipulated like per atom quantities? For example, with a mixture of spheres, I could do the following computation if I would like to:

variable velx atom vx
variable vely atom vy
variable sqvel atom sqrt(v_velx^2+v_vely^2)
compute vel all reduce ave v_sqvel

Hi,
I am new to LIGGGHTS and have been having trouble finding information on how quaternions are calculated.

This is the second time to ask this question since nobody answered the first and I really need an answer for this issue!

I'm trying to make a triaxial compression test in two scripts. First, generating particles using insert/stream in a cubic region then unfix all walls and save a restart file. Second, fix new servo walls and apply equal pressure from all walls except the base wall and after reaching the target confining pressure, I only increase the pressure of the upper wall to apply vertical compression on the sample. I use kp = 1, ki = 0, kd = 1e-6.

I'm modelling a sample with superquadric particles. Particles are inserted using insert/stream into a cubic cell. When I measured the porosity (void fraction) of the whole sample after insertion, it's found to be 0.35 (sample is very dense). How could I increase this value in order to get looser packed samlpe.

Thanks for your time.

Hi all,

i have a question regarding the friction models that can be used in Liggghts.
coefficientFriction - this is the static or internal friction
coefficientRollingFriction - rolling friction as in the name

Where can we define a sliding friction coefficient? Is there an implemenation of sliding friction in Liggghts? I have found 1 post where coefficientFriction is regarded as the sliding friction Coefficient, which should be wrong?!

Hi
Can anyone guide me on how to install LPP for LIGGGHTS 3.8.0 in Ubuntu 20.04.LTS. as I am finding error message as python 3 is installed instead of Python.

Thanks in advance.

Hi, I have a question about the value of the force and how it come from.

I did the simulation and dumped the file for contact and atom.

I get the atom data using 'dump aa all custom time id type x y z vx vy vz fx fy fz ...'

And the contact data using 'compute bb all pair/gran/local id pos force_normal' and dump it.

Hello Everybody,

I am absolutely new to LIGGGHTS. I tried to run template script on cluster. When I run from cmd it works, but when I try to integrate it with slurm, I get this error:

ERROR: Invalid command-line argument (../lammps.cpp:271)
Can anyone help me to solve this problem?

Thanks in advance,
Omid.

Hello LIGGGHTS forum.

Really thank you for your help. You guys have been amazing in my research journey.

I have one more question regarding cohesion.

I am trying to add cohesion model in my simulation. Right now I am using following model as mentioned below:

pair_style gran model hertz tangential history #Hertzian without cohesion

Right now I am using inclined surface with atom style granular.
I went through liggghts tutorial regarding `gran cohesion sjkr model`. But couldn't find the exact way to apply cohesion with value.

Hello LIGGGHTS forum,

I am confused regarding region bc coordintes.

Could you please explain me about the coordinates which are used as 0.0, 0.0. 0.15, 0.05, 0.12 ?

In this command :

region bc1 cylinder z 0.0 0.0 0.012 0.01 0.05 units box

I know this is a silly question. I went through the LIGGGHTS tutorial but still couldn't make my self clear?.

Thank you