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[lammps-users] Shear Flow of non-spherical particles
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[lammps-users] Shear Flow of non-spherical particles

From: Sina Haeri <s.haeri@...652...>
Date: Thu, 18 Dec 2014 10:39:07 +0000

Dear lammps users,

It sent this message yesterday but seems that the email was not sent
correctly and the thread is empty. So I am sorry if you are recieving
this for the second time.

I'm trying to simulate shear flow of non-spherical
particles (dumbblle shape) using fix rigid and granular package
(version: 9-Oct).
The particles are create from two overlapping spheres (see attached
figure) and initially configured in a 25x25x25 lattice (using
with a vol fraction of 0.6

I am using the following script for my simulation

units           si
atom_style      sphere
boundary        p p p
newton          off
comm_modify     mode single vel yes

#Read the Cluster of compound particles and add mol property
fix                  addMolecule all property/atom mol ghost yes
read_data       dumbells.dat fix addMolecule NULL Molecules

#Relax the particles
pair_style      gran/hooke/history 2000 NULL 50 NULL 1 0
pair_coeff      * *

velocity        all create 1e15 1234 loop geom

neighbor        0.003 bin
neigh_modify    delay 0 every 1 check yes

timestep        1e-5
fix             1 all rigid molecule

run 30000

#Remove Previous Settings
unfix        1
uncompute    1
uncompute    2

reset_timestep    0

#New Seetings
change_box    all triclinic remap

pair_style      gran/hooke/history 2000 NULL 50 NULL 0.5 1
pair_coeff      * *

timestep    1e-5

fix        1 all rigid molecule

fix         shearRun all deform 1 xy erate ${shearRate} remap v units box

run ${NSTEPS}

I expect to get a linear velocity profile but I get an S shape profile.
This is independant of the time step size. I have attched velocity
profile results for three different shear rates. At very low rates
(${shearRate}~1) the profile is almost linear but this quickly changes
to an S shape by slightly increasing the shear rate (${shearRate}>2).
The simulation also seems to have reached steady state since I tested it
with two different ${NSTEPS} with larger nstep twice the smaller one.

I appriciate any ideas or suggestions from the developpers or the community.

Regards - Sina



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Attachment: twoParticle.png
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