LIGGGHTS® - User Forum

Hi,
I have been trying to solve for ellipsoidal and line type particles. I searched in many forums and available tutorials, but I could not find the syntax for the atom_style parameters for these types of particles. The only particle type I was able to find was a sphere and granular with a sphere template. Is there any place where I could find the fix parameters for particle insertion like this for other types of particles:

fix pts1 all particletemplate/sphere 15485863 atom_type 1 density constant 2500 radius constant 0.015

I'm using fix adapt to fill a volume to the correct packing fraction after an insert/pack operation:


compute rad all property/atom radius
variable diam atom c_rad*2
variable size atom ramp(1,4)*v_diam
fix grow all adapt 1 atom diameter v_size scale no


I'm trying to insert two populations of particles in the same region using:

fix insS all insert/pack seed 179426369 distributiontemplate pddS &
insert_every once overlapcheck yes all_in yes volumefraction_region $(v_fillIniS) region &
reg
fix insL all insert/pack seed 32453423 distributiontemplate pddL &
insert_every once overlapcheck yes all_in yes volumefraction_region $(v_fillIniL) region &
reg

Just confirming that the units for Young's Modulus are in the relevant simulation units.
ie.
for micro units, pg/(um*us^2)
The documentation does not specify whether it gets scaled or not.

Thanks,
Thomas

Dear all,

I was looking at the documentation of the hertz model and have a question about the following equation.
K_n = 4/3 Y*(R*delta)^(1/2)

I derived this equation from the hertz model and find the equation should be
K_n = 4/3 Y*R*^(1/2)delta^(3/2)

This result is also given by the wikipedia and some other papers.

Could anyone tell me which one is the correct one? This may have a great influence when the large cohesion is added.

Thanks,
Brian

Hello, everyone!

I have installed LIGGGHTS on our university cluster (CentOS 7.4) with VTK turned off. The compilation was complete and lmp_auto file was created.
I have copied the lmp_auto file to the folder with chute_wear example to check how it is working. However, when I tried
mpirun -np 4 lmp_auto < in.chute_wear
the following error appeared:

Dear all,

Hi, everyone
when I use the rolling_friction epsd3 for my simulation, I got the following error:

ERROR: Could not locate a fix/property storing value(s) for rollingStiffness as requested by rolling_model epsd3. (../modify_liggghts.cpp:411)

The epsd3 model request the definiton of rollingStiffness, but it is calculated as k_r = coeffRollingStiffness*k_n*rmu*rmu*reff*reff in the liggghts doc.

Any suggestion what I missed in my script.

# Material properties required for granular pair styles

Dear LIGGGHTS users,

I recently use rolling frition model epsd for triaxial test simultation. When I create a bulk of particles, and let them settle under gravity, high omega is observed for alomst every particles, up to 500 rad/s. My particles have a radius from 1..10mm.

Can anybody help me with this.

neighbor 0.0005 bin
neigh_modify delay 0

hard_particles yes
# Material properties required for granular pair styles

Hello!

I am doing simulations of powder compaction using artificial gravity. I have been simulating them under 2000g. So once this gravity is applied, particles start to disappear as in the screenshot attached. You can see that number of particles reduced from 7884 to 7508 and then it stays constant. Reducing the time step from 1e-6 to 1e-7 seconds has increased the final number of particles, but only slightly, so some particles are always disappearing.