LIGGGHTS® - User Forum

Dear all,

I just implemented the Van Der Waals force model on LIGGGHTS. In order to validate my numerical model, I need to know the non-contacting van der Waals force between two interacting particles in LIGGGHTS.

Actually, I tried to compute the aforementioned force using 'compute 1 all pair/gran/local id force' in LIGGGHTS, however, the results only contain some contacting forces.

I would like to know whether LIGGGHTS can output or compute this type of non-contacting force now? If not, I need to write a 'fix' function to write this kind of forces?

Hi, all,
I'm running a simulation with some problems on the mesh. I use a STL file as the wall of my model. I got this STL from the CFD ICEM software. However, the STL exported from this software seems to be bad. The LIGGGHTS gives neither warning or error on this STL file.

The warning is like the following line. It just warns, but the script can run without a hitch. Does it matter? Does this warning have impact on the result?

WARNING: Fix mesh: Mesh contains highly skewed element, moving mesh (if used) will not parallelize well (../surface_mesh_I.h:657)

Hello, all,
I'm trying to use the fix massflow/mesh command to count the particle flowing trough the outlet of my model. I use the following code in my script.
# Mass flow measurement
fix massflow all mesh/surface file Outlet.stl type 3
fix mass all massflow/mesh mesh massflow vec_side 1.0 0.0 0.0 count once file ../DEM/post/Particlemassflow*.txt

Hello
I am trying to print mass of the particle in a particular region but I am unable to get. Please guide me

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?

post deleted

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,