LIGGGHTS® - User Forum

I am trying to analyze the effect of packing style on the granular motion. A particular region needs to be filled by packed bed of specific style (bcc, fcc, hcp).

Is there any way or inbuilt command in LIGGGHTS to handle this task? On the other way, I think it is possible to replace the particle coordinates in dump file with the coordinates (that suits the specific style of packing)
generated by third-party package. But still, if there is a simple way to do the same?

Hello everybody,

Dose anybody know how can we restore a value defined by variable in a simulation (it is scaler defined after the simulation results) and then use the value in a new simulation? I use write_restart to save the simulation but it seems that the value defined by variables can not be saved. I can manually input the variable in the new script but it is time consuming. Any good ideas?

Jeremy

Right now, shape of particle is a sphere. Can user define a shape of particle like cube, ellipsoid etc. if yes, could you please explain how to do it.

Thanks in advance.

Simon

Hello, has anyone successfully been able to calculate and visualize the force chains within a multi-sphere body?

I'm using the "hybrid granular molecular" atom style with a "fix rigid molecule" command, and am curious to see the force within the conglomerations/molecules and how that changes over time, i.e. with contacts.

Hi,

I am trying to simulate the following code, but when I entered dump command xyz(dump("dump*")).many()
It is showing that no dump file specified . Please tell me where it went wrong.

units real
dimension 2
boundary p s p

atom_style atomic
neighbor 2.0 bin
neigh_modify delay 5

# Create Geometry
region boundary block 0 100 0 80 -0.25 0.25 units box
create_box 3 boundary
mass 1 60.1
mass 2 60.1
mass 3 60.1

Dear Friends,

Currently I have started to use pair_style gran/hertz/history/stiffness model in my DEM simulation.
In the LIGGGHTS manual I find that the specified parameters are multiplied by some other parameters like: the effective mass and radius, sqrt (delta n) .

I took a look on the source code and copy/paste them here:

double polyhertz = sqrt(ri*rj/(ri+rj)*deltan);

kn = polyhertz*k_n[itype][jtype];
kt = polyhertz*k_t[itype][jtype];
gamman = polyhertz*meff*gamma_n[itype][jtype];
gammat = polyhertz*meff*gamma_t[itype][jtype];

I am looking for an exmaple of cold spray or a similar sample. It also
appreciates that you can give some advice. I am beginner on Liggghts but there is very
interesting to know it.

Thanks in advance.

Simon

How can I implement "mesh/surface/stress/servo" using primitive walls?
I say this because in the "mesh/surface/stress/servo" command, we have to use "File Filename.stl", but I do not have any .stl file in my simulation and I control the simulation domain by primitive walls.

I am looking forward to hearing from you.

Regards,
Rasoul

I have two cad files in my simulation. The one is auxiliary just works as splitter and need not to be visible in final results. I know I am using line "dump dumpstl all mesh/stl 200 post/dump*.stl" in my script which applies to all meshes, and by changing the group-ID the issue can be handled. But I don't know how to assign group-ID to stl files (or mesh groups).

Anyone please help...
An example would be really appreciable.

Thanks in advance.

Hi all,

I have a general question for the LIGGGHTS user who are experts on DEM and also on CFD or SPH or Lattice Boltzmann.

I want to model the behaviour of a liquid (water or oil) between 2 surfaces constituted by DEM particles (i.e., spheres). So as to obtain the pressure and the friction induced by the liquid properties within the contact on the DEM surfaces.

I don't know which fluid method I can use with DEM part of LIGGGHTS to perform this simulation because I don't know SPH and CFD very well.