LIGGGHTS® - User Forum

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.

Hello together,
I have only an short question.
Is it possible to read a value, which is used in the fix porperty/global command, from an external file.
If it is possible, it would be nice if someone can give me an example.

Best regards
RobertG

Dear all,

firstly as a new user I like to say Hello!

Although I understand the ideas of DEM pretty well, my programming skills with respect to C++ are practically in-existent. From what I understood by reading the manual and 1 or 2 entries in the Forum, my problem may need some programming, but please correct me, if I am wrong.

Hi all,

I am reading atom positions from a text file without any error to run a rotating mill case. When I visualize my results I see that the particles are in the correct position but only the ones in contact with the geometry of the mill move due to its motion.

I wonder if this is because I have not set any velocity in my text file.

So I tried to add velocity in the file, in a correct format apparently but I cannot find the way for LIGGGHTS to understand it.

Any comments would be appreciated. I am attaching the data file used.

Thanks in advance,

Dear All,

I have two doubts about cohesion model sjkr.

1) In the cohesion model, what is the reference for cohesion energy density values? How do we select the values
for cohesion energy densities? Can we calculate it, if we know the properties of liquid and solid?

2) Cohesion model uses JKR model, and it adds only an additional normal force. What about tangential force?

Any help will be much appreciated.

Thanks,
Narendra

Hi

In my cylinder model, the particles are not filling the annular region. Iam just getting a packed form. I don't know what is wrong with my inputdeck. Iam attaching the input deck. log file and model.

Regards
Hari

Hi,

during a run I plot the stress on a servo wall which is always around 10178 (last value ) but always at the last step after the run this value switches to 8408. I dont understand why this happens. has someone maybe an idea that could solve this?

Is it possible to get the dissipation energy per collision as an output?

Thanks

I am trying to simulate a suction action using a dynamic region and fix addforce. The problem occurs that the dynamic region moves partially, but not the entire length of the simulation region. I am using the variable function ramp, over 100k time steps, but it looks to be only evaluating it over 20k steps.

I am using LIGGGHTS 3.1.0.

Any help is appreciated.

-Scott

Dear liggghts users,

I use hertz contact model to simulate the sandy soil and the young's modulus is 20e9 for sand. But the contact force is so large with this 20e9 modulus so that it keeps telling too many neighbor bins message. So I am thinking to use a very small timestep. Here comes to problem, if I use small timestep like 1e-8 or 1e-9, the simulation is time consuming. So what can I do to enhance simulation time and make the simulation no error by that I mean reasonable?
Hope anybody could guide me!!! Deeply appreciated!!

Best wishes
xiaobaishu