LIGGGHTS® - User Forum

Hi colleagues,

I am facing a problem about outputing the magnitude and average of contact force, but failed.
To obtain the contact force, I use command:
compute fc all pair/gran/local pos id force (the 10-12th values are the contact forces on x,y,z directions)

Then I use:
variable avefc atom sqrt(c_fc[10]^2+c_fc[11]^2+c_fc[12]^2)
to calculate the magnitude of contact force.

Hello all,

I need to invoke a python script during the run time of the simulation . The script has to be invoked in every timestep. Is there a possibility to do that?
I know the other way around (python->Liggghts) is possible. But I need to compute some paramaters outside liggghts at each and every timestep and I need to use that data again in the simulation. So please suggest me some ideas on this.

Thank you .

Hi everyone,

I have recently implemented a modified heat conduction model in LIGGGHTS. If anyone is interested in using and discussing about this piece of work, uploaded in ArXiv, https://arxiv.org/abs/1809.01379, please drop me an email weijing.dai@sydney.edu.au.

Cheers
Weijing

I have read the paper by Podlozhnyuk et al. (2017) and curious about the contact force calculation.

Referring to Fig. 6, it is shown that different results of adopting different radius method.

And I have written a script to examine the results.

However I have got the results of the volume equivalent sphere. And I could see the big difference from the FEM results if I keep increasing the overlap.

Is there any comment on it?

Or it would be appreciated if you could give your experience on examine it?

Kind regards,

Hello,
Is there a way implement a particular force exerted from the fluid side on the particle to be integrated using implicit time integration, ASIDE from the dragforce. It seems there is a possibility to integrate ONLY the drag force implicitly:
https://github.com/CFDEMproject/LIGGGHTS-PUBLIC/blob/master/src/fix_cfd_...

Hi everyone,

i am working on a liggghts simulation of a plastic extruder for my master thesis.
On my adventure with DEM i noticed that the soft particle approach wants to have only small overlaps between particles (< 0.5%d).
In my real life case the particles are getting deformed in their way through the extruder. Wich leads to some questions:

1)How does a Youngs Modulus exceeding the limit of 5e6 Pa change my simulation. (in older versions i had to add "hard-particels: yes")

Hi,

I need a clarification. I am simulation triaxial tests on soil. I am using Servo walls on the sides and top to give a constant confinement and move my bottom mesh with a velocity.

To print the volume, I calculate the position of the walls.

Hello all, I am new in LIGGGHTS, and I need help)
Can I have an example of a simulation where multisphere particles breakdown due to mutual abrasion?

In my project I'm going to simulate abrasion breakdown of particles in fluidizied bed reactor, and I have no idea how to do it.

Thanks, Rustam.

Hi,
I wanted to know that in the following command line:
fix pressdown topwall aveforce 0.0 -1.0 0.0

-1.0 is applied in the -ve y direction to each atoms of the group topwall or to all the atoms together?

Sincerely,
Sounik

Hello experts!

I have some problems with the convergence of the contact point of two touching superquadrics. The contact between two superquadrics remains undiscovered if the blockiness value exceeds a certain treshold. For the attached example the superquadrics with blockiness value n_1 = n_2 = 5 touch each other but if the blockiness is n_1 = n_2 = 10 there is a complete overlap without contact recognition. So far I have not been successful in solving the problem by using a smaller timestep or an alternative neighbor bin size value.