LIGGGHTS® - User Forum

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:

Hi,

is it possible to calculate a variable with circular dependency?
like

variable a equal v_a+1

and I want to evaluate the variable each timestep. So I need to use the variable in a command where it is used every timestep?
Is there a smart funktion that calculates the variable every n timesteps without printing or saving the variable somewhere?

Thanks
Joshua