LIGGGHTS® - User Forum

Hi, i want to rotate a region i defined for post-processing purposes. I use:

region reg1 cylinder y 1.0 -1.0 0.35 4.75 5.25 units box rotate 1.0 0.0 0.0 0.0 0.0 1.0 0.0

However on execution i get the error "illegal region command". What is wrong, i thought i could rotate a region as described in "region command" documentation.

Thanks!

Hello all,

I am trying to model a confined cylidrical box which consists of uniform particles. The particles have to be compressed to a stress of 100N and then under the stressed state, I have to apply sinusoidal load. I am using a mesh to represent the plate at the top. I use mesh/surface/stress/servo to apply the force 100N on to the particle. I cross checked the force by looking at the force values of the mesh plate.

Hello Friends, I have found from the documentation that the following property definitions should be used in order to use hooke/stiffness model.

fix m1 all property/global kn peratomtypepair 1 1e03
fix m2 all property/global kt peratomtypepair 1 0.0
fix m3 all property/global gamman peratomtypepair 1 0.0
fix m4 all property/global gammat peratomtypepair 1 0.0
fix m5 all property/global coefficientFriction peratomtypepair 1 0.0
fix m6 all property/global coefficientRestitution peratomtypepair 1 1.0

So I'm trying to simulate a vibratory feeder using the "wiggle command" to move particles up a 3 degree incline. I used a cylindrical path to drop the particles into and its supposed to shake and move the particles upward the 3 degree incline. For some reason I was not able to model an inclined ramp so I modeled it flat and modified the gravity vector to simulate an incline. The particles climb up the ramp at a 5 to 6 degree incline but not at a 3 degree incline. Can someone look at my code and see if possible my gravity vector is incorrect or some other settings needs to be adjusted?

Hi!

Hello Friends, Greetings. We all know that particle simulations are high dissipation systems. Lets say we have a cuboid container defined by 6 primitive planes oriented along X-Y-Z axes, filled with spherical particles to a certain height, gravity acting along Z. When this system is fluidized (that is, particles are set into motion),

1. How can we calculate energy that is being lost due to (a) collisions, (b) friction?

I'm tracking instantaneous net energy of the system using compute totRotKE all erotate/sphere and compute totLnrKE all ke.

Hello Friends, Greetings.

Lets say we have a cuboid container defined by 6 primitive planes oriented along X-Y-Z axes, filled with spherical particles to a certain height, gravity acting along Z. When this system is at rest,

1. How can we calculate net downward force acting on bottom wall (as a single value)? This must be equal to weight of all particles combined.
2. Is it possible to get force field on this bottom wall? This must be uniform, vectors pointing downwards (assuming flat or constant hFill) and sum of all field must be equal to weight of all particles.

hi i need to charge particles the set command charges atom or molecules i need granules charged to insert them in an electric field to change the particles directions if anyone could help me it would be great i could not find a solution i wanna perform the same thing as in the electrostatic example in the site https://www.cfdem.com/electrostatics thanks in advance hope someone helps me i am stuck for weeks on this thank you in advance

I'm trying to run a simulation like that in Podlozhnyuk et al. (2017) Fig. 7, where superquadric particles are piled up in a container. However, in a small test with 138 I find that the particles fall towards the bottom surface then start to 'dance around' and they never come to rest (see attached animation). I've tried altering the simulation parameters, including adding coefficient of rolling friction, but the problem still occurs. Could anyone suggest what might be incorrect or missing in the script (below).

Many thanks !

Liggghts version 3.8.0

Hi,all

I need to define two “pair_style” using “pair_style hybrid”,however,I faced an error.

ERROR:Incorrect args for pair coefficients

Here is the part of my input script.

pair_style hybrid gran model Hooke tangential history gran cohesion easy/capillary/viscous
pair_coeff * *

Thank you.