LIGGGHTS® - User Forum

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

Can anyone please tell me the name of the contact search algorithm used in LIGGGHTS-Public?? and how contact search algo is implemented in LIGGGHTS??

Hello guys,

I am fairly new to LIGGGHTS and DEM in general, so you will probably read my name a few more times in the future.

I created an input file and ran a few simulations where I insert particles using insert/pack in a box shaped region inside my domain to for a plateau. So far so good. In the next step I would like to use the end result of one of these simulations as the starting state for any following simulation, so that I don't need to waste precious simulation time on building the same plateau on every run. (I hope this makes sense so far.)

Hi everybody,

I'm using the easo model and am trying to monitor the liquid content of the particles. I read in an older version of LIGGGHTS documentations that the f_surfaceLiquidContent[0] command could work but it does not explain how. Any help regards this matter is greatly appreciated.

Thanks in advance.

I'm struggling to find a command that gives me the current timestep of my simulation. I'm trying to create a variable that depends on the current timestep of the simulation but for the life of me, I can't find any reference to such a command in the LIGGGHTS documentation.

Does such a command/variable exist?

Thanks in advance!

Hello everybody,

I have a question about the rotate keyword in the region command.
If I use the rotate keyword, is the region constantly moving or is it a stationary region, just rotated by v_theta every timestep?
And if I want to calculate the angle v_theta form the rotating velocity omega, how do I specify the time?

Thank you in advance.

Hello,

beforehand I am very new to this topic. I want to use LIGGGHTS and later CFDEMcoupling to simulate a coaxial rheometer which in theory is a hollow cylinder with a rotating inner wall.

My question: How do I create this geometry in LIGGGHTS without importing a mesh file?

My ideas were on the one hand to create two cylinder regions. For the outer wall an inward facing region and for the inner wall an outward facing region.
On the other hand an idea was to create a region inside the outer wall and create the inner wall with a fix.