LIGGGHTS® - User Forum

Hello all,

I would like to simulate particles in a container that are stirred by to stirrers. The container is available in an stl file and so are the two stirrers. So, in total, I've got three stl files. I assume that splitting the whole geometry into 3 parts is necessary, since the two stirrers are supposed to have different angular velocities and the container is at rest.

While importing the second stl and and applying the fix wall/gran/hooke I get the following error message:

ERROR: There must be only one fix wall/gran with style 'mesh/gran'

Hi Christoph,

I am developing a new contact model. In my case as you suggested, I took the pair_gran_hooke_history like base.

For the first step, I only replaced the name of class PairGranHistory by PairLatticeHistory.

I have two files pair_lattice_history.cpp and pair_lattice_history.h. In the file .h, I change:

#ifdef PAIR_CLASS
PairStyle(lattice/history,PairLatticeHistory)
#else
#ifndef LMP_PAIR_LATTICE_HISTORY_H
#define LMP_PAIR_LATTICE_HISTORY_H

Thus into my simulation file, I can use this key word: pair_style lattice/history 1 0

Hi all,

I have no idea how liggghts generates stress-control compression tests, although I know that liggghts has a powerful engine to conduct strain-control ones. However, it is necessary to do stress-control if want to conduct drained triaxial test because I need to maintain the confined stress constant.

Could someone told me how to do stress-control compression or give me some suggestions?

Thanks!

Best,
Tong

Hi all,
I think there are some problems with the implementation of the tangential spring in the pair_style gran/hooke, especially for soft particles where the overlap between the particles gets high.
So far the relative rotational velocities between 2 particles are calculated by using the radius of the particles:

wr1 = (radi*omega[i][0] + radj*omega[j][0]) * rinv;

The force application point for the tangential forces also lies on the radius of the particles:

torque[i][0] -= radi*tor1;

Hi all!
The region command in liggghts is static but it becomes dynamic when we apply wiggle command. Is this possible that we apply the wiggle command but the region should remain static. Can anybody help?
sajjad

Hi all,

I have this small error when I run my simulation :

85589 atoms
82223 atoms in group A
3366 atoms in group B
ERROR: Length not sufficient for variable youngsModulus

Do you know thir error ? How can I resolve this error ?

For information, if there is only one group of atoms (i.e., 85589 atoms in group A), the simulation runs.

Regards
JF

Ps: the Youg's modulus is defined for all groups (i.e., fix m1 all property/global youngsModulus peratomtype 1.e5)

Hi,
Why I can not find same scales of mesh object in LIGGGHTS when I import it made in Maya? I created mesh in cm in Maya and export it in STL. Then import the same in LIGGGHTS but it doesn't show the same scales of hight and diameter as that of Maya's. I have to rescale the object in LIGGGHTS for required scales. It takes a lot of time. Furthermore, height-diameter ratio will not remain same when it was in Maya.
Thanks,
Ram

Hi all,

I have the objective to modify the neighbor class in order to load a neighbor list via a text file. I need your opinion to do this in compliance with the previous developments in LIGGGHTS. The interest is to extend LIGGGHTS to perform lattice beam simulations.

Therefore:
I am thinking to add a new style : enum{NSQ,BIN,MULTI,TXT} in the files : neighbor.cpp and neigh_list.cpp

I am thinking to add a new request: int latthistory in the file neigh_request.cpp

Hi,

I am creating spheres so that they initially intersect with walls. I get the following message

WARNING: Dangerous build in triangle neighbor list.

What is the consequence of this? I am getting a memory error I don't understand and I wonder if this is the reason...

Thanks for all the help,
George

Hi all,

I want to simulate a granular flow in a shear cell. Therefore I have a axis-symmetric geometry. To save computing time I want to simulate only a quarter of the ringshaped geometry by using quarter periodic boundary conditions in angular direction. Is there a possibility to use such a boundary condition in the current build?

Thanks
Yansan