LIGGGHTS® - User Forum

Hi all,

I am simulating a group of particle bonding together ( like a string). I divide a string (or fibre) into a number of balls. By this way, I need to define the bonding peroperties (kn; ks) among these balls so that they can be created and also be broken. I got a nice suggestion from Christian (Richti) in terms of granular bond package. Could anyone share with me more information about this package? how can I get and install it? Does it work on public version of LIGGGHTS? DEM simulation would be strongly limited without bonding.

Thanks,

Does anyone have any good methods for moving from euler rotations in x,y,and z worldspace, to the axis-angle format needed by liggghts? The method I've been using isn't as robust as I'd like.

Cheers.

Hi All,

When i am using rolling friction in my model, it is giving the following error;

ERROR: Fix wall/gran (id geometry): Unknown argument or wrong keyword order: 'rolling_friction' (../fix_wall_gran_base.h:96)

I have used the following statement in my input script

fix geometry all wall/gran model hertz tangential history mesh n_meshes 3 meshes cad1 cad2 cad3 rolling_friction cdt

Without rolling friction my script is working fine.

Any help will be much appreciated.

Thanks,

Narendra

Hey ,

I tested a bit the rolling friction model epsd2 and read also the paper from Ai, Chen, Rotter and Ooi.
Where the limiting spring torque is calculated by:
nu_rollfrict*R*F_n

If you consider now that the maximum torque from rolling in one contact that can occur is:
nu_friction*R*F_n

Dear all,

I have problem with rotating the geometry stl file in LIGGGHTS.
without rotation everything is working well and no problem occurs but when I insert the following rotation line to the script:

fix movecad1 all/move/mesh mesh cad1 rotate origin 0. 0. 0. axis 0. 1. 0. period 1

this error happens:
ERROR: Could not find fix group ID (modify.cpp:657)

Dear LIGGGHTS users,

I encountered some problem when compling LIGGGHTS using cfdemCompLIG command in Mac OS X.
The issue seems to occur during compilation of sub-libraries for liggghts.
Detailed logs are attached. Here is some additional information that I tried to get from compileLIGGGHTS_lib.sh:

Hi,
I am trying to run a simulation with a wide disparity in particle sizes. For the same, I wanted to use the "neighbor binsize multi" option which would be more efficient then using a single bin size for all particles. However when I run the simulation with the "multi" option, no neighbour list is created. The "multi" option also seems missing in the neighbor_gran.cpp file. Has this option, which is available in lammps, not carried forward in liggghts?

Thanks,
Tapan

Hi all,

I would like to know how particles are placed on a wall (primitive and/or mesh). Are they put on a regular network or randomly?

Thank you guys,

Hi,
i have a question about the calculation of the contact force for particle-wall contact.
For example, if i use the Hertzian model, which radius will be inserted for the wall in the prefactor of the equation
sqrt(delta*(Ri*Rj/(Ri+Rj))*(...)?
Is the force calculated the same way, like for particle-particle-contact, at all?

Hi! i'm relatively new to liggghts, and i want to compute the contact area in a cone crusher. So far i'm using the "compute wall/gran/local contactArea" command, to store the information, unfortunately, i don't know how to use only a single mesh wall to compute the contact area.

The code that does the wall gran, computation and the dumping is: