LIGGGHTS® - User Forum

Hi all,

I wonder if it is possible to introduce a directional bond between particles. Unlike cohesion, Im looking for some kind of bonding which is effective when there are contacts only in specific directions of the particles.

Thanks,

Ozgur

question:

fix 1
run 1000 upto

unfix 1
fix 2
run 2000 upto

unfix 2
fix 1
run 3000 upto

unfix 1
fix 2
run 4000 upto

unfix 2
fix 1
run 5000 upto

repeat ..

I want to know what command or skills may use for the alternate cycle as above example. Welcome any suggestion or advise.

thank you in advance.

best regards,
xinze

Hi all,

I have a question- Am I correct in assuming that there can only be one meshgran wall in a simulation?
If yes I have a slightly complex situation- I have a cube bounded by 6 flat surfaces in which I have my granular sample. I want to move the top surface only AND measure separately forces on the top, bottom and side surfaces.

Hello Christoph!

I ran into a problem using three atom_types -- two for particles and one for the walls -- which leads to my question:

Hello Christoph,

I wonder which commands can complete the reduction of particle diameter over time in a specified region just as you have gived example lammps_particleReduction_.wmv in this web. I think it is maybe lammps's some command or tips, Could you kindly give me help or instruction?

Thank you.

best regards,

leexz

Hi,

When I use
pair_style peri/lps for the pair style, I get this error:
ERROR: Invalid atom style

I wonder if it is possible to use this pair style with LIGGGHTS or not.

Thanks,

Ozgur Keles

Hi LIGGGHTS Users,

we try to create a cone-style insert region (just like a hopper) with the pour/dev/packing command. The input script looks like this:

#particle insertion region
region ins_cone cone z 0.04 0.0 0.01 0.065 0.09 0.16 units box
region ins_cyl cylinder z 0.04 0.0 0.065 0.08 0.16 units box
region no_ins_region intersect 2 ins_cyl ins_cone side out units box

...

#region and insertion
fix ins all pour/dev/packing 1 distributiontemplate pdd vol ${alphastart} 10 overlapcheck no region ins_cyl regionexempts 1 no_ins_region

Dear LIGGGHTS users!

Attached you find a (not very sophisticated) Python script to produce a data file as input for a new simulation generated from a specified time step of a dump file of another calculation. Maybe this is useful for somebody as a starting point for similar problems.
The dump/custom command in the first simulation includes "id type type x y z ... radius mass".

Christian

PS: You have to rename the file extension to .py

Hi everybody,

I am interested in a simulation of a big sphere containing a many smaller particles. I tried this simulation by adding particles of a defined radius on a regular lattice. The problem is that this reguar structure works a a kind of crystalline system with slip planes when I try to deform it.

However I'd like to try another approach by adding the particles without a lattice with the "pour command". Is there a way to use this command with a sphere as the input region (and not a cube or a cylinder)?

regards,
Martin Koester

Hi all,

For the gran/hooke pair style the documentation says that the equation for the elastic constant is:

k_n = 15/16* ...

In the code the elastic constant is calculated as follows:

kn=(16./15.)*sqrt(reff)* ...

So which one is right, the code or the documentation?

Thanks
Yansan