LIGGGHTS® - User Forum

Dear all,

For a CFDEM project I tried to model interacting particles in a converging channel, to predict clogging behavior. To realise this I suspect to need cohesion behavior of the suspended phase.
In a 2d situation, also for a pure DEM calculation I get triangle neighbor list problems, even for very small time steps (1e-12) and particle 'explosion'; particles disappear when colliding.

Is cohesion in 2d unobtainable or is something else wrong? Attached my case and stl files.

Particles are quite large in comparison to channel size, just to check the behavior.

Both fix move and fix nve "count" as integrators, and if an atom is under both it will give us this warning. However, what if motion is only partially fixed? Then we still need an nve/nvt/npt integrator, so the warning must be generated.

Even if all DOF are fixed, it would be just a slight waste of time and not a serious accuracy problem.

Hi,

I am trying to simulate rocks that tend not to roll, is there a way that I can model translating only particles?

I tried using the rolling friction model with a high value of rolling friction;

pair_style gran/hertz/history rolling_friction cdt

with

fix m6 all property/global coefficientRollingFriction peratomtypepair 1 0.5

Hi Christoph,

my student Esperanza stumbled upon an inconsistency. For heat transfer area correction this command must be used:
fix heattransfer all heat/gran initial_temperature 300 area_correction yes
However, the docu suggests to use
area_correction values = on or off

Cheers,
Moritz

Hi,
is there a fix for pouring or inserting particles of complex shapes (like rods or rice grains), defined using the multisphere method or via fix rigid and pair_style hybrid granular molecular?
If not, is there such an utility for LIGGGHTS in preparation which will be made available for public usage in a forthcoming version?
Best
Eric

Hello:

I'm a novel user of LIGGGHTS, first of all I'd like to apologise for my simple question. I'd like to generate ten particles that their position, diameters and densities are different. How could I implement that in Liggghts?

Thank you in advance

Hi,
Is there a way to turn off the interaction between a frictional wall (imported using "fix mesh/surface") and a selected group of atoms in a simulation? I want the wall to act as boundary only for some atoms in the simulation and not for others based on the atom type. I tried using the "neigh_modify exclude" command but it does not seem to work for walls.

Any suggestions would be appreciated.

Thanks,
Tapan

Hi,

I just pulled the latest version (2.0.6), the particles are now changing temperature due to the hot conveyor. I have attached a little mpeg for anyone that is interested. Happy to have this working now!

Thank you,

Kirk

I just noticed that coord/gran doesn't appear in LIGGGHTS 2.0 - is this a feature that will be re-integrated, or was it removed deliberately?

Thanks! Mark

Hello,

I believe there is an error in shear modulus formula in the manual for pair_gran. Instead of

1/G*=2(2+nu1)(1-nu1)/Y1+2(2+nu2)(1-nu2)/Y2

there should be

1/G*=2(2-nu1)(1+nu1)/Y1+2(2-nu2)(1+nu2)/Y2

If we take two equal materials so nu1=nu2=nu and Y1=Y2=Y then accordind to your formula G*=Y/[4(2+nu)(1-nu)] and k_t=8G*=2Y/[(2+nu)(1-nu)], however according to the literature, k_t=2Y/[(2-nu)(1+nu)].