LIGGGHTS® - User Forum

LIGGGHTS® related topics can be discussed here: discussion about models, installation, feature requests and general discussion

Rotating drum example

Submitted by jagan1mohan on Sun, 11/08/2020 - 21:22

Hello friends, greetings.

I'm looking for the rotating drum tutorial in which the wall is made of particles. By any chance, any of you have a copy of in.* file?
Or
Any such files where we have a wall of particles moving / rotating? I want to understand the setup. Eagerly waiting for your reply.

Thank you,
Jagan Mohan.

Counting collision frequency between different types of particles

Submitted by achraf on Sun, 11/08/2020 - 16:37

Hi
I would like to count the collision frequency between different types of particles in each time step.
i have 16 types of particles :
i did manage to count for each type, but what i need is to count for example :
Between Type 1 and Type 1, between Type 1 and Type 2 ...., between Type 16 and Type 16.
here is my code :

property/global command for multiple atom types

Submitted by SHUBHAM AGARWAL on Thu, 11/05/2020 - 00:17

Hi
In my simulation, I am using three types of atoms (say 1,2,3) I need to define the contact stiffness between each of them (E1,E2, E3)
For that I am using the following
fix m1 all property/global youngsModulus peratomtype ${E1} ${E2} ${E3}

As far as I can understand, this command has assigned a young modulus to each of the particles. How it takes care say when atom 1 and 3 come in contact. Is there a way to assign contact modulus like that? I tried peratomtypepair but it did not work.

Thanks
Shubham

Region orientation and Prism command

Submitted by SHUBHAM AGARWAL on Tue, 11/03/2020 - 20:47

Hi
I am using LIGGGHTS - flexible fibers version
I am defining a prism region using the following command:
variable dummy2 equal 1.01*${beam_length}

region bc_blade prism ${dummy2} ${dummy2}+${blade_particle_diameter} -${blade_particle_radius} ${blade_particle_radius} 0 ${blade_length} 0 0 ${blade_particle_radius} units box

All the variable are defined tin the code, however I am encountering the following error;
Illegal region prism command

How it can be solved??

Counting collision frequency between different types of particles

Submitted by achraf on Mon, 11/02/2020 - 18:01

Hi
I would like to count the collision frequency between different types of particles in each time step.
i have 16 types of particles :
i did manage to count for each type, but what i need is to count for example :
Between Type 1 and Type 1, between Type 1 and Type 2 ...., between Type 16 and Type 16.
here is my code :

Implementation details of the Nase viscous force model for liquid bridges

Submitted by paul on Fri, 10/30/2020 - 16:25

Hello everyone,

I was wondering about one of the implementation details of liquid bridge models, namely the definition of the minimum separation distance ratio, which is required to have values > 1 and is recommended to have a value of around 1.01 according to the documentation

Translational/Rotational Energy of Molecules

Submitted by RonMexico on Thu, 10/29/2020 - 18:29

I am creating rigid bodies from groups of spheres using, for example,

fix 1 all rigid molecule

From doing some simple tests with two spheres setup as a diatomic molecule, it appears that LIGGGHTS will always output the total energy - translational + rotational - for ke. I want to separate this energy into rotational and translational pieces in the thermo output. LAMMPS seems to have had ways to do this with compute temp, but that does not appear to be a thing in LIGGGHTS. I tried using erotate, but that does not seem to correlate with what I need at all.

group/group command for granular pair

Submitted by SHUBHAM AGARWAL on Wed, 10/28/2020 - 20:59

Hello
I am currently using LIGGGGHTS-flexible fibers version for granular bonds.
In my simulation I have 2 groups (web & blade), and I want to calculate the force that web exerts on the blade. For that I tried the following command:
compute force_inter blade group/group web

However, I am encountering the error saying that "Pair style does not support group/group".
In the contact style, I am using the following:
"pair_style gran model hertz tangential history "

Can someone please help me to resolve this

Thanks

the overall number of collisions between different types of particles

Submitted by kodai on Wed, 10/28/2020 - 18:57

I would like to count the overall number of collisions between different types of particles.

Suppose we have 3 types of particles

So what i need is the total number of collisions between each type, between type 1 and type 2 , between type 1 and type 3, and between type 2 and type 3, Is there a way to do this?

Do i have to make some changes in the source code of liggghts or use a predefined liggghts command .

Ps: i have 20 different type of particles.

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