LIGGGHTS® - User Forum

Hello dear liggghts community members !

I'm interested to simulate using the SPH pairstyle cooling and subsequent solidification of a mixture of 2 liquid phases.
I know there's a heat conduction fix in liggghts , but i'm not sure if the sph particle parameters actually depend on temperature\pressure so the material properties could change appropriately to liquid->solid phase transition.

Is liggghts capabale of simulating solidification ? What would be a good start towards this direction ?

Hi Christoph,

I was wondering, how do you generate non-spherical particles in LIGGGHTS according to the mesh scanned from Laser Scanner?

1) Simply fill in single particle inside the mesh manually with minimum number of particles?

2) or fill in automatically by means of certain algorithm according to the points or surfaces?

Hi Friends:

I don't know why I can not completely fill the container. Here is the snip of my code.

boundary p p f
region reg cylinder z 0.0 0.0 10 0.00 50 units box
create_box 1 reg
fix m1 all property/global youngsModulus peratomtype 5.e9
fix m2 all property/global poissonsRatio peratomtype 0.45
fix m3 all property/global coefficientRestitution peratomtypepair 1 .3
fix m4 all property/global coefficientFriction peratomtypepair 1 .5

pair_style gran/hertz/history 1 0 #Hertzian without cohesion
timestep 0.00001

fix gravi all gravity 9.81 vector 0.0 0.0 -1.0

Hi all,

I'm trying to write the total torque to an output file. For doing this I've read:
(1) Torque on axle exerted by particles (Forum-Post at 27.07.2011)
(2) Compute pair/gran/local (Forum-Post at 16.12.2010)
(3) fix print command (in the LIGGGHTS-doc)
(4) fix mesh/gran/stressanalysis command (in the LIGGGHTS-doc)
(5) fix_mesh_gran_stressanalysis.cpp (sourcecode)

But I do still not know how to write the total torque out. The question in (1) describes exactly what I will do.

I am interested in creating or modifying an existing pair style (such as pair_gran_hertz_history) so that it uses different contact behavior as a function of the number of touching neighbors, or coordination number. Does like this sound like something that is possible in LIGGGHTS? How and where is the coordination number stored in the program? Could I use it as a variable in the pair style's C++ file?

Thanks in advance,
Will

Hi There,

I'm having a problems when running my simulations. The following error happens:
ERROR: Lost atoms: original 1976 current 1971
I have tried to change some parameters like reducing the time step, reduce the entry surface size and so, but I couldn't find out what causes this problem.
The case is simple, it is a box in the top of a conveyor. I'm using particles distribution from 60 to 250 mm diameter.
I'd appreciate any help about what could cause this problem.
Best regards,
Marc

hi all ,
using fix ave/spatial i was able to generate a file with results that looks like :
#Bin corrd1 corrd2 Ncount vy
,,
,,
,,
this file has all the bins that fill my simulation box
how can i dump a file with has only the bins in a specific region (section of my simulation box) !?

thankx in advance
Yaman

Hi,
I noticed sometimes when I read .vtk file from pizza with paraview that I have:

Error reading ascii data. Possible mismatch of datasize with declaration.

and I can't see the fields I have in the dump file.
It happens mainly when I move stl file into my particles.
Does anyone known why? I tried different paraview versions (3.8, 3.10.1 3.12) but it's the same.

Thanks for any help

Andrea

hey

I am sure it is something I have done wrong, but I was running a simulation where something is rotated, and then a mesh is to be removed. The fixes that were in place were:

fix cadcyl all mesh/gran 2cmcyl.stl 1 1 0 0 0 0 0 0
....
fix rotcadcyl all move/mesh/gran rotate 0 0 0 0 0 1 1.0 cadcyl

when my simulation got as far as unfixing both of these I then got the error message:
ERROR: Atom type must start from 1 in granular simulations

and I am unsure as to why this has happened as I do not see how unfixing both of these is related.

sorry to bring it up again

by importing some *.stl file from cad I get this error

ERROR: STL import failed at triangle #0 (line 1), degenerated triangle?
I have read in some previous posts the answer that "check if the triangle is degenerated"
I don't know what is meant by this ? what should I check for in that stl file.
I do not get this error when i import cylinder, but upon importing sphere bodies I get this error.
thanks