LIGGGHTS® - User Forum

My models can't endure with high pressure those particles will penetrate inside the models (particle go through the model when simulate at high pressure i can understand because it makes sense but some times low pressure also). In actually it shouldn't penetrate. I would like to ask you how to make model strong? I think it should has some parameters in LIGGGHTS that can make a wall strong enough for endure with high pressure simulation.

Thank you,
terces907

Another beginner question: I'd like a normal distribution of particle sizes with a mean of 0.000925m and a standard deviation of 0.1.

I've tried this:
fix pts1 all particletemplate/sphere 1 atom_type 1 density constant 2900 radius gaussian number 0.009525 0.1
fix pdd1 all particledistribution/discrete 1. 1 pts1 1.0

but I get this:
ERROR: Probablity distribution: mu-3*sigma < 0, please increase mu or decrease sigma (probability_distribution.h:169)

Do I need to put sigma = (0.009525*0.1)?

Hi, Christoph:

I am doing a simulation involving chemical reaction of particles. In the simulation, I have to update some material properties, such as Young's modulus, Poisson's Ratio, and friction coefficients.... These coefficients must be changed according to their early values (on the last time step), so that I can implement a calculation like:

S_new=S_old+1

When I do it by using the 'variable atom' commands, errors always take place. This algorithm is easy to implement in C++ or other languages. But, it becomes a wrong statement in Liggghts. Do you know why?

This is a beginner question, but I haven't had much luck with it. I have some moving and some static geometry. I would like to only dump the moving geometry to keep the file size down. Ideally I would like to dump all moving geometry parts into a single stl. I'm not sure the syntax to do this. In the meantime I've tried to export each part separately using this:

dump dumpstl body mesh/stl 160 post/body_*.stl
dump dumpstl1 shaftR mesh/stl 160 post/shaftR_*.stl
dump dumpstl2 shaftL mesh/stl 160 post/shaftL_*.stl

I simulated the bubble reactor and I consider the bubbles as dem particles. The bubbles came out from the inlet at a certain velocity, the diameter of bubbles are treated as constant. How can I insert the bubbles to make them fit the certain velocity conditions? Can the insert_stream command works it out?

I simulated bubbles as dem particles, which lifted in the water and came out at the top of the difined box region. How should I set up the boundary conditions of outlet to make the bubbles disappeared when they came out the box? Which command can I use or should I modify the source code to realized it?
thank you for you help!!

thanks,
Zhao

Hi everyone,

I am trying to deposit particles with the ''fix deposit'' command, but I do not know how to define the radius and density of the particle. I tried to use the ''create_atoms'' and ''set'' command, but the dump file shows the radius is not the same as I defined. Is there anyone know how to modify it?

Thanks.

Hello Everyone, I want to simulate a bubble column which bubbles spray out from a gas distributor into water.

Bubbles were considered as the discrete phase and their flow behaviour was simulated using DEM. The water phase was continua phase which was simulated using Euler method. The diameter of bubbles was supposed to be a constant(5mm).

I want to use Herz-Mindlin Granular contact model to complete the simulation. I just consider the bubbles the same as any other solid particles simply.

Can I use liggghts to simulate the bubbles contact?

Hello cfdem community,

I am currently trying to setup a granular simulation which drags a cylindrical intruder through a bed of granular material. ideally the granular material would be setup to act like glass. i can get the simulation to run on a large scale (5cm beads) but when i set the granular material size to 5mm and scale the bed size down appropriately the granular material will never settle in the bed it will simply bounce around forever.

my input script is as follows:

# Moving cylinder mesh example

atom_style granular
atom_modify sort binsize 0.0025

Hi,

I find that the actual mass inserted is about three times greater than the requested mass when using insert/pack with a lognormal distribution. It is about 10% greater than the requested mass when using a gaussian distribution and slightly greater when using a uniform random distribution. Using volumefraction_region instead of mass_in_region gives about the same results. I can live with a few percent error, but it looks like something is very wrong with the mass calculation for the lognormal distribution. Here is a short script that demonstrates each case.

David