LIGGGHTS® - User Forum

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?

Hi all,
I'm trying to run a 2D simulation. I'm using the 1.4.6 release.
I found 3 main problems:
- the choesion model doesn't work for 2D models. How is it possible to take in account it?
- the particletemplate/sphere + pour/dev/packing does not work with 2D analysis but only with 3D. So I switched to pour/legacy LAMMPS command. Is this wanted or is it a bug?

Hi all!
I am new to LIGGGHTS and want to simulate granular gas. As suggested by Christoph that LIGGGHTS can be used to simulate granular gas but the time-step has to obey the Hertz criterion.
But i dont know how to calculate the value of time step which obey the Hertz criterion especially with vibrating boundaries.
If somebody can help me or guide me, i will be thankful. I am not finding a proper way to calculate time step value.

Maz

Dear All !
I have a basic question " can LIGGGHTS be used for the simulation of dilute granular media i.e. especially for the granular gas?" if yes, is there some special limitation about time step or some other limitations ?

Anyone help, i will be thankful.

Sajjad

Hey

I wanted to rotate a mesh using the fix/mesh/gran, but I didn't want the rotation to be instantaneous. Is there anyway to define a spin up dw/dt until it reaches the desired w? I'm pretty sure there isn't but thought I'd ask?

One work around would be to alter the rotation every few timesteps, but this would be clunky, and would make for a messy input file. So, assuming this capability isnt there, how easy can I program this in, and where can I do it?

Jay