LIGGGHTS® - User Forum

Hi,

I'm using the epsd2 model for rolling resistance. I know that it adds a resistance moment against rotation, but does it also transfer this moment to the next particle? So is the torque transferred from one particle to the next?

Kind regards
Joshua

Dear all,

I was trying to understand how the overlap can be measured in LIGGGHTS if we have two spheres in collision. I know that I can find the value of the overlap through this equation (from the positions):
Overlap= d-r ;

But actually I am looking for the original equation that has been used in the source to compute the overlap for any collision.

I would be very grateful if you could provide me with any information (equation or paper or book) about computing the overlap in DEM .

Many thanks,
Abdul

Hi,
I want to model a wire in a spiral scheme (like a wire-reinforced membrane) that encloses some particles. the wire should interact with particles and should be able to deform . If bond atomstyle is applicable here what should I add to the code to effectively simulate the interactions. Is there any example in this case?

Any suggestion will be regarded
mojgan

Hi
I am trying to generate a very loose packing by radius expansion method. I pack smaller particles randomly and then assign a friction coefficient (i.e 0.24 in my case) and allow the particles to grow up to a desired radius. consequently, the consolidation procedure is modeled. The method does not result in a very loose pack and the void ratio does not differ significantly from that in a specimen with a friction coefficient of 0.0. the code is as follows

Hello,

Can anyone let me know like what are the limitations/restrictions of LIGGGHTS code?
Like particle size, is this code valid for nano-sized particles also?
I know there is "vol_limit" , is there any specific answer for choosing "vol_limit < 1e-12" ?
If I change to "vol_limit < 1e-20", is the code still valid? or do I need to change any properties?

If possible please let me know the limitations of LIGGGHTS code.

Thank you.

Hi ,

I tried to use hybrid granular molecular to simulate multisphere systems, the atoms are successfully read, and I used fix rigid infile to define the center of mass, and moments of inertia. Initially, the non-spherical bodies are uniformly distributed in the simulation box, with a volume fraction of about 0.1, and the first few thousand time steps are running fine (time step = 1e-6), however, the simulation box will increasing after several thousand of time steps, and I can see the total amount of atoms are decreasing.

Hi all,

I am running a rotating mill with 1 atom, velocities and positions are read from a read_data file. It runs and the behaviour of the atom is as expected, but the time it takes to finish the simulation is way too long, obtaining 0.23 seconds per iteration.

If I keep all the same settings but insert the particle with the insert/stream command, the time is much smaller, such as 0.005 seconds per iteration.

Hello,
I recently updated my LIGGGHTS-Version to 3.2.
One of the many features is the temperature can be assigned when the particle are created.
But unfortunately, I can't find any examples of this function.
If someone can give me one, it would be great.

Best regards
RobertG

Dear all,

attached to the post you find an input deck with my attempt at creating a rotating drum which is just a cylinder of a fixed diameter and length. In order to achieve wall friction I inserted a fix,namely

fix cyl_wall1 all wall/gran model hertz tangential history primitive type 1 ycylinder .09 0.0 0.0

The computation runs smoothly, but doesn't show what I expect. For those of you with greater experience my error might be obvious, but let me explain my thinking:

I want to simulate shear mixing in a twin-screw geometry, but I am facing two problem:
1. after particle insertion, they don’t see the STL walls, so they often cross kneading discs, and other time the barrel, which I have not been able to understand why. Doubting the role of smaller time step requirement, I check time step suitability using check/timestep/gran to be sure that time step is not undesirable, changed location of particle introduction to avoid wall interference, but still not able to figure it out.