LIGGGHTS® - User Forum

Hi all,

I already read the documentation about the contact model but I still can't get it.

(https://www.cfdem.com/media/DEM/docu/gran_model_hertz.html)

I understand the equation about the contact force but how can we calculate the normal overlap, tangential overlap,

normal relative vel, tangential relative vel in the LIGGGHTS?

I searched the code 'contact_model_hertz.h' for detail but can't understand how those are calculated.

Can anyone explain this for me?

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Dear community!

I'm trying to conduct first part the Triaxial test -confining. So , For this I used Fix deform command to compress sample. I used Deform because walls should be periodic. And now I don't know how to manage compression to achieve constant Normal force or stress.

Does anybody know what kind command should I use ?

I would like to calculate the number of particles that hit a wall. I have implemented the 'compute conts all contact/atom' with the fix that allows the collisions to be summed (https://www.cfdem.com/forums/counting-particle-particle-collisions), but this is limited to sphere/sphere contacts. Is there a simple way to count wall-sphere contacts?

I am trying to import geometry with the help of following command. However, the imported geometry (after dumping by simulation run) looks distorted and different that the original stl file.


fix screen_stl all mesh/surface/stress file Geometry/Screen_VFinal.stl type 2


I tried with precision and heal settings also but to no luck

fix screen_stl all mesh/surface/stress file Geometry/Screen_VFinal.stl precision 0.00000000000001 heal auto_remove_duplicates type 2


Hello,

Hi,
As i am new to DEM simulation using liggghts ,

Based on bonded superquadric particle , we have developed a flexible film. Our objective is to make the flexible film as realistic as possible. For example I need to make a flexible film having properties as similar to a PVC film. Here I have 2 questions,

Hi all LIGGGHTS users,

I've encountered an issue with particles escaping out of the nozzle mesh wall. My aim for the simulation is to create a steady state powder flow out of the nozzle which i've uploaded the CAD file. I used ovito as the visualization tool and i noticed the no. of particles started decreasing as the powder flow hits the entry of the nozzle. After zooming, i saw a few particles flying out of the nozzle walls. Any idea how to avoid this? I assumed there is something wrong with my 'fix wall/gran' command.

Thanks in advance.

Hi, I am using some very wide grain size distributions (gsd). I have discretized the gsd as input to liggghts. I am using large prime numbers as seeds (which is a strange constrain) and all.

Hi everyone !

As my model requires to include DLVO Forces, I have to include pair_style yukawa/colloid into LIGGGHTS. For this reason I have followed previous Forum threads:
https://www.cfdem.com/forums/how-install-colloid-package
and
https://www.cfdem.com/forums/adding-new-force