LIGGGHTS® - User Forum

Hi everyone,

I'm trying to set up a simulation with 3 spheres clumped together, exactly as seen in LIGGGHTS Features > Non-spherical particles > Example - pouring a continuous stream of non-spherical particles, where can be seen particles made of 3 spheres glued together.

I'm exploring some possibilities to do a modification of this study http://www.nt.ntnu.no/users/skoge/prost/proceedings/ecce6_sep07/upload/1... by simulating a packed bed with non-spherical particle as my PhD study. My idea is starting with 3 spheres glued and then move on with different particle geometries.

Hi all,

I have so far been running LIGGGHTS with more-or-less "large" particles (mm/cm), but now want to move towards the size that interests me, around ~1 µm or so. However, if I try to use fix particletemplate/sphere and fix particledistribution/discrete to generate small particles I get an error which seems to arise from a hard-coded limit:

if(volume_expect < 1e-12) error->all("Fix template/sphere: Volume expectancy too small");

in fix_template_sphere.cpp.

Hi. I want to use mesh/tet and insert/pack features.
I use in.insert_pack example file as basic for my simulation.
But I get an error when I use own insertion region geometry file instead of test.vtk:

LIGGGHTS 1.4.1 based on lammps-10Mar10
Created orthogonal box = (-1 -1 -1) to (1 6 2)
1 by 4 by 1 processor grid
Fix particledistribution/discrete (id pdd1): distribution based on mass%:
pts1: d=5.000000e-02 (max. bounding sphere) mass%=30.000000%
pts2: d=3.000000e-02 (max. bounding sphere) mass%=70.000000%

Hi all,

I had a look at the gran/hook/history/simple pair_style today. I thought that this pair_style should make you able to directly set the values for kn, kt, gamman and gammat depending on the contact-partners. So I was wondering why the values for the damping coefficients (gamman and gammat) are multiplied by meff. The same modification is done for wall-contacts.

I think that should be changed otherwise you have to take the multiplications into account when you set the values in the input-script.

Regards,

Yansan

Is it possible to use a gaussian distribution of radii for the particletemplate/sphere command? The documentation says it is possible but I am getting the following error:

ERROR: Random style gaussian not available for radius

My pertinent code is:
fix pts1 all particletemplate/sphere 1 atom_type 1 density constant 2500 radius gaussian 0.0003 0.00005
fix pdd1 all particledistribution/discrete 1. 1 pts1 1.0

Thanks,
Will

Hi all,

I have been playing with aggregated particles using a hybrid granular/molecular pair style, and am now introducing heat flow into the simulation. In the current implementation if I exclude the aggregates from neighbor calculations, there is no heat flow between member particles (this, of course, makes sense!). If I remove this exclusion, then heat does indeed flow, but at a rate determined by the thermal properties and the initial overlap when the aggregates are created (i.e. determining the contact area).

I would prefer either to be able to either:

I have an idea about vizing the superquadrics using paraview.
first, creat a superquadric source;
then, read your vtk files including particles postions;
the last, use glyph with custom sources. The following image shows what I have done.

Chen

Hi!
Is it possible to insert group of particles, so that their initial velocity would be against gravity field? I've tried it with

fix pour/dev

command, but it gives me an error message:
ERROR: fix pour: z-velocity must not not be <0.

Thanks,

Timo

This probably relates to this problem, but I've posted a new topic to attach some images...

I have just tried to verify the coordination number for some simple packings (in this case simple cubic). I have computed and dumped the coordination number using computer coord/gran. I was expecting a coordination number of 6 everywhere apart from at the edges...

Hi,
What is the best technique of making dense granular packings in liggghts?
Thanks in advance
Amrita K