LIGGGHTS® - User Forum

Hi all,

I'm trying to write the total torque to an output file. For doing this I've read:
(1) Torque on axle exerted by particles (Forum-Post at 27.07.2011)
(2) Compute pair/gran/local (Forum-Post at 16.12.2010)
(3) fix print command (in the LIGGGHTS-doc)
(4) fix mesh/gran/stressanalysis command (in the LIGGGHTS-doc)
(5) fix_mesh_gran_stressanalysis.cpp (sourcecode)

But I do still not know how to write the total torque out. The question in (1) describes exactly what I will do.

I am interested in creating or modifying an existing pair style (such as pair_gran_hertz_history) so that it uses different contact behavior as a function of the number of touching neighbors, or coordination number. Does like this sound like something that is possible in LIGGGHTS? How and where is the coordination number stored in the program? Could I use it as a variable in the pair style's C++ file?

Thanks in advance,
Will

Hi There,

I'm having a problems when running my simulations. The following error happens:
ERROR: Lost atoms: original 1976 current 1971
I have tried to change some parameters like reducing the time step, reduce the entry surface size and so, but I couldn't find out what causes this problem.
The case is simple, it is a box in the top of a conveyor. I'm using particles distribution from 60 to 250 mm diameter.
I'd appreciate any help about what could cause this problem.
Best regards,
Marc

hi all ,
using fix ave/spatial i was able to generate a file with results that looks like :
#Bin corrd1 corrd2 Ncount vy
,,
,,
,,
this file has all the bins that fill my simulation box
how can i dump a file with has only the bins in a specific region (section of my simulation box) !?

thankx in advance
Yaman

Hi,
I noticed sometimes when I read .vtk file from pizza with paraview that I have:

Error reading ascii data. Possible mismatch of datasize with declaration.

and I can't see the fields I have in the dump file.
It happens mainly when I move stl file into my particles.
Does anyone known why? I tried different paraview versions (3.8, 3.10.1 3.12) but it's the same.

Thanks for any help

Andrea

hey

I am sure it is something I have done wrong, but I was running a simulation where something is rotated, and then a mesh is to be removed. The fixes that were in place were:

fix cadcyl all mesh/gran 2cmcyl.stl 1 1 0 0 0 0 0 0
....
fix rotcadcyl all move/mesh/gran rotate 0 0 0 0 0 1 1.0 cadcyl

when my simulation got as far as unfixing both of these I then got the error message:
ERROR: Atom type must start from 1 in granular simulations

and I am unsure as to why this has happened as I do not see how unfixing both of these is related.

sorry to bring it up again

by importing some *.stl file from cad I get this error

ERROR: STL import failed at triangle #0 (line 1), degenerated triangle?
I have read in some previous posts the answer that "check if the triangle is degenerated"
I don't know what is meant by this ? what should I check for in that stl file.
I do not get this error when i import cylinder, but upon importing sphere bodies I get this error.
thanks

Hi There,

I was doing a few tests with LIGGGHTS and I saw that I can't do 2 dynamics of the same style at the same time for the same geometry. I'm trying to use 2 wiggles (move/mesh/gran) for the same geometry, but it looks like the second command overwrites the first one, so I can't have the dynamics I was expecting.

Hi all,
I'm trying now the new 1.5 (downloaded from git)
I fount that the compute eraotate/sphere command warks stangly
It calculates Rot. En. = 24662670.
Using the same in. file the 1.4.6 version calculates Rot. En. = 3.0077387e-08 (that is more familiar with my case).
Maybe is there some bugs in the 1.5? Or the command is changed?
Thanks

Hi all,

I am trying to run a simulation with a hybrid granular and sph model. My first attempt was using the sph example case (liggghts 1.5.0) and replacing
atom_style sph
by
atom_style hybrid sph granular
I ended up with the appended input file. I'd expect that the system behaves exactly like the sph example but
* instead of creating a wave that moves smoothly back and forth the particles just fall in -z direction
* also I get an error: ERROR on proc 0: Particle on or inside fix wall/region/sph surface

Did I make a mistake? Is SPH incompatible with the hybrid atom style?