LIGGGHTS® - User Forum

Dear Forumers:
I noticed a new feature form the announcement of the LIGGGHTS2.3 release, which can calculate solid resident time distribution in a region- "Added new fix property/atom/tracer and fix property/atom/tracer/stream commands along with a new compute nparticles/tracer/region command for the calculation of residence time distributions". Howerer, I can not find a test case or a tutorial to use this feature, and I also wonder how to ouptut the results as simulation processes. If anybody knows, please give me some clue. Thanks in advance.

Hello,

I am discovering a very interesting function "mesh/surface/stress/servo" which enables to apply a force on a wall.

fix servo all mesh/surface/stress/servo file plate.stl type 1 com 0. 0. 0. ctrlPV force dim z set_point -10 vel_max 1.

First, I would like to know, what is the parameter 'set_point' in your example ?

Then, I would like to apply a force (10N) on two walls (top and bottom) to perform a compression test in the Z-direction.

Hello all,

I'm interested in simulating a horizontally rotating bin where particles leave through an orifice geometry that I have designed.

Hi all

I've been reading the manual in order know how to speed up the simulation. If I increase the number of processors to running the simulation I'll be able to reduce the pair time. is it the best solution to achieve my aim?
Can anybody tell me the steps that I have to follow?

best.

I'm having a frustrating issue at the moment. I set up a simulation (at the moment with basically no particles), and then import an ascii stl mesh (produced in meshlab) with the following line:

fix MT all mesh/surface file MT.stl type 1 rotate axis -3.832567 0.000000 2.832567 angle 17.365650

When I look at the output, the mesh has rotated, but it has also become larger. Am I doing something wrong here, or is this a bug?

tar attached containing full input script and original stl mesh.

Attached is a little Fortran code for calculating the center of mass and moment of inertia for a clumped particle.

Regards,
Chris

Hi,

is it possible to calculate and dump the center off mass for clumped particles ? I tried compute com/molecule and varius dymp-styles but without success. Or is there a post-prozess option in pizza ?

Thanks,
Christian.

Hello, Christoph,
I try to use the latest version of LIGGGHTS 2.3.2, but it doesn't work. Then I tried with an example from Liggghts - meshGran, and it doesn't work either. I uploaded the output and error meassage files. Could you take a look? Thank you!

Hi everyone,

I'm confusing with cohesion energy density in the pair_gran_hooke_history. As I understand cohesion energy density is the work needed to separate the whole volume of particle in contact. So how to calculate cohesion energy density if Van der waals adhesion is taken into account? And where is cohesion energy density in original JKR model?

Many thanks for your help!

Best regards,

Duy

Has anyone ever made an atom property (or assigned it to a region, changed its type, etc) based on a conditional statement?

For instance, if I set some threshold of particle force, say...
variable crit_force equal 50
then i find per/atom values of force magnitudes
variable mag_force atom (fx[i]^2+fy[i]^2+fz[i]^2)^0.5

from there I'd like to say something like...
if "${mag_force[i]} > ${crit_force}" then &
[set the atom, i, into a group, change the atom to type 2, etc.]