LIGGGHTS® - User Forum

Hello everyone,

I am working on liggghts, and I generated a particle packing in the geometry by command insert/stream, after particles become stationary in the bottom, i would like to make the packing position fixed and not be moved anymore. In other words, after packing formed, we treated it as a wall.

I tried the command fix freeze and fix setforce, but the particles not acted force tend to overlap with each other, and it is unexpected.

Do you know how to realize this ?

thanks.

I am simulating shaking grains in the vertical direction and I would like to speed up my simulation. I can use up to 24 cores. Since, the motion is predominantly in the z direction, should I maximize number of cores in this direction? Also, I noticed if I reduced the number of cores and let liggghts decide the optimum distribution, 20 cores make it faster instead of 24. I thought it was counter-intuitive but then again it could just be how liggghts distributes it. What should I do?

Hello everyone,

I want to simulate with a volume fraction of 0.4288 but this would lead to unreasonable high numbers for maxattempt to work.
So deactivated overlapcheck, but then the manual says the overlapping configuration has to be relaxed.
My problem: there is no word on how to do this.

Can anyone tell me how to relax properly? ;)

Thank you in advance.

Hello everyone,
I am a student doing a project work, as part of my task I need to calculate traction when my sample come in contact with soil. Here the problem is particles are inserted and now there is no contact of my sample with my particles as sample is just at the surface but due to clearance between sample and particles there is no contact. Can anyone help me with this to make contact between sample and particles.
Thanks & regards.
Rohith.

Hello Everyone,
I am a student working on a project, here I need some help regarding particles to be inserted. In my project I need to fill an bowl with flat surface full of particles but I don't know how many particles to be inserted to fill the bowl. I would be glad if anyone help me out of it.
Thanks in advance.

Hi all,

I am trying to fill a container with multisphere particles. Since filling the container will take a very long time (over 48 hours), I created a restart file. However, when I try to restart the simulation to continue filling the container, an error comes up.

First, it was
ERROR: Fix multisphere (id integr): requires an 'atom_modify map' command to allocate an atom map (../fix_multisphere.cpp:343)

So I added the line: atom _modify map array sort 0 0

Hello everyone

I got stuck with working of servo wall during the confining process in my triaxial simulations.
I do want to maintain the 1 MPa stress on the each of the servo wall( i have six faces) before going for the shearing process

Hello everyone,

before I ask my question and describe my problem, I want to summarize what I did so far and what I experienced, so that it might make more sense.

I installed LIGGGHTS-Public and Paraview according do the Tutorials and Guides in this forum and the doccumentation (using make auto). Everything works fine, I can run simulations and they look good so far.

I want to use thermal conductivity as a function of temperature. For instance, as simplest form,

variable kt equal temp
or
variable kt equal f_Temp

and

fix ftco all property/global thermalConductivity peratomtype v_kt

But this gives “ERROR: Could not find thermo custom fix ID”

LIGGGHTS manual is a bit confusing about thermo_style. Unlike LAMMPS, liggghts thermo_style command does not take “temp” as an argument. I can dump f_Temp values by just using f_heattransfer argument in thermo_style, when I use a constant conductivity.

I am using servo wall for the triaxial compression. I specified the 10000 N force on the inplanes wall as the target force and target velocty is 0.0001,
Howevervr timestep is 10-7 (looking for quasistatic simulation)
PID contants are
Kp = 0.01
Ki = 0
Kd =0
However the forces on the servo wall is not converging wrt to the specicified taget value
It is continuously increasing as specidief in the below figure
What would be possible solution to converge the target force on wall ??

Thanks