LIGGGHTS® - User Forum

Hi everyone,

the case I am simulating consists of a bunch of particles stirred in a tank. The geometry of the stirrer is available in stl format.

I would like to calculate the torque exerted on the stirrer or the axle moving it, respectively. I've played around with fix mesh/gran/stressanalysis and its capabilities are almost what I need. Is there a way in liggghts to integrate the stresses such that I get the resulting torque on the axle?

Thanks for any comments.

Best regards,
Moritz

I have tried to calculate coordination number for a compact data-set with the command compute/cord/gran and got a very low number so I decided to write separate code and do this calculation. I considered two particles to be neighbors if their distance is less than or equal to the sum of their radii and got a reasonable result. I don't know why there is such a difference.

Hey Christoph,

I don't get where the coefficientFriction is used in gran/hertz/history formula, according to the formula given in pair_gran.html file there is no need to this quantity.

I am having an issue with particles falling through a wall. Particles begin in a cylinder and are poured directly downward into a block. Most of the particles are caught by the block, but on the first iteration about half of the particles fall through the block when they are first inserted. Is there a reason that these particles fall through? Would the problem have to do with the specified regions or possibly the fix wall/gran/hertz/history?

Thanks
Kirsten

I created a new geometry using AutoCaD and exported it as ASCII stl file. I am using the file in my LIGGGHTs input script. When I run the simulation I get the below error message

Importing STL file 'geometry.stl'
Solid body detected in STL file
End of solid body detected in STL file.
ERROR: STL import failed at triangle #0 (line 1), degenerated triangle?

Can anyone please tell me what this error is about and how to fix this error?

Regards
Vinodh

Hi Christoph,

I am thinking about using the Particle segregation in a slot geometry example for my simulation after doing some changes to it to fit to our simulation.

It will be of great help if you can please share the input script for the Particle segregation in a slot geometry example that is there on the LIGGGHTs website.

Thanks!

Jai

Hi,

I've updated my system using the current version of LIGGGHTS and CFDEM. Compiled both without any problems (using openfoam 2.0.0). Starting liggghts without problems but when the first run command would be started liggghts crashed. The error is looking like:

Setting up run ...
[simserver:25567] *** Process received signal ***
[simserver:25567] Signal: Segmentation fault (11)
[simserver:25567] Signal code: Address not mapped (1)
[simserver:25567] Failing at address: (nil)
[simserver:25567] [ 0] /lib/libpthread.so.0(+0xf8f0) [0x7f519337c8f0]

I am using the latest version of liggght and tried to output the result of the
"comput pair/gran/local pos id force" command with the following dump command :
dump dmp all local 1000 post/dump.force c_10[1] c_10[2] c_10[3] c_10[4] c_10[5] c_10[6] c_10[7] c_10[8] c_10[9] c_10[11]
I can not run the code on more than 1 by 1 by 1 processor grid. as soon as I use 2 by 1 by 1 processor grid or 2 by 2 by 1 processor grid I receive some errors like mpirun noticed that process rank 1 with PID 9127 on node ... exited on signal 11 (Segmentation fault)

Hi,

I want to print the stress or pressure of a single atom into a file. When I put the following lines in the input script, no error occurs:

compute stress all stress/atom
variable xx equal c_stress[1][1]

However, trying to print the xx stress component of atom 1:

fix print all print 100 "${xx}" file xx.txt

results in the following error:

ERROR: Per-atom virial was not tallied on needed timestep

I don't understand this ERROR message even after refering to the LAMMPS documentation.

Best regards
Thomas Wagner.

PS: I found a solution in the forum: