MULTISPHERE PARTICLES BECOMES COHESIVE

Submitted by kashif saeed on Sat, 06/17/2017 - 14:30

Hi,
I have a problem with multisphere particles simulation.
when i use same case for simple spherical particles mixing, my results are good but when i used multisphere particles ( 2 or more sphere clumped together to form particle) then particles becomes cohesive and no mixing occurs between particles. i created multisphere particles according to code given in following link
https://www.cfdem.com/media/DEM/docu/fix_particletemplate_multisphere.html

can any one help me why particles become cohesive as i am not using any command or property that give cohesiveness to particles.
thanks in advance

Forums:

Westbrink | Mon, 06/19/2017 - 08:57

Hi Kashif,

could you upload your input script please.
Then it is easier to give you a support.

Regards

kashif saeed | Wed, 07/05/2017 - 18:45

Following is sample code for the multi sphere with three spheres forming a rod like a shape. kindly tell me why particles become cohesive.

atom_style granular
atom_modify map array
boundary f f f
newton off

communicate single vel yes
processors 1 1 1

units si

region cyl cylinder z 0. 0. 0.075 0. 0.320 units box
create_box 2 cyl

neighbor 0.003 bin
neigh_modify delay 0

#Material properties required for new pair styles

fix m1 all property/global youngsModulus peratomtype 5.e6 5.e6
fix m2 all property/global poissonsRatio peratomtype 0.45 0.45
fix m3 all property/global coefficientRestitution peratomtypepair 2 0.95 0.95 0.95 0.95
fix m4 all property/global coefficientFriction peratomtypepair 2 0.05 0.05 0.05 0.05
fix m5 all property/global coefficientRollingFriction peratomtypepair 2 0.01 0. 0. 0.

#New pair style
pair_style gran model hertz tangential history #Hertzian without cohesion
pair_coeff * *
#physical characteristics of particles:

fix pts1 all particletemplate/multisphere 123457 atom_type 1 density constant 2456 nspheres 3 ntry 1000000 &
spheres -0.0025 0. 0. 0.0015 0. 0. 0. 0.0015 0.0025 0. 0. 0.0015 type 1
fix pdd1 all particledistribution/discrete 63243 1 pts1 1.0

fix pts2 all particletemplate/multisphere 123457 atom_type 2 density constant 2456 nspheres 3 ntry 1000000 &
spheres -0.0025 0. 0. 0.0015 0. 0. 0. 0.0015 0.0025 0. 0. 0.0015 type 2
fix pdd2 all particledistribution/discrete 63243 1 pts2 1.0

#import mesh from cad:
fix zwalls1 all wall/gran model hertz tangential history primitive type 1 zplane 0.020
fix zwalls2 all wall/gran model hertz tangential history primitive type 1 zplane 0.33
fix cylwalls all wall/gran model hertz tangential history primitive type 1 zcylinder 0.072 0. 0.

# Import mesh
fix cad2 all mesh/surface file meshes/impeller.stl type 1 curvature 1e-5

# Imported mesh as granular wall:
fix mixer all wall/gran model hertz tangential history mesh n_meshes 1 meshes cad2

fix integrate all multisphere

#gravity

fix gravi all gravity 9.81 vector 0.0 0.0 -1.0

#Timestep
timestep 0.00001

#Area where the particle are introduced from is set:

region factory cylinder z 0. 0. 0.068 0. 0.3 units box

#thermo setting
compute 1 all erotate/multisphere
fix ts all check/timestep/gran 1000 0.1 0.1
thermo_style custom step atoms ke c_1 f_ts[1] f_ts[2] vol
thermo 1000
thermo_modify lost ignore norm no

#defines how the insertion is going to be done:

fix ins1 all insert/rate/region seed 123481 distributiontemplate pdd1 &
nparticles 3500 particlerate 7000 insert_every 1000 &
overlapcheck yes vel constant 0. 0. -2.0 region factory ntry_mc 10000

run 30000
unfix ins1

fix ins2 all insert/rate/region seed 431524 distributiontemplate pdd2 &
nparticles 3500 particlerate 7000 insert_every 1000 &
overlapcheck yes vel constant 0. 0. -2.0 region factory ntry_mc 10000

run 40000
unfix ins2

#make a dump of particles and the stl file
dump dumpstl all mesh/stl 1000 post/dump*.stl
dump dmp all custom 1000 post/dump.1 id type type x y z ix iy iz vx vy vz &
fx fy fz omegax omegay omegaz radius
dump dmpvtk all custom/vtk 1000 post/dump*.myforce.vtk id type type x y z ix iy iz vx vy vz &
fx fy fz omegax omegay omegaz radius
run 10000

#rotate central shaft
fix movecad2 all move/mesh mesh cad2 rotate origin 0. 0. 0. axis 0. 0. 1. period -2

#run 5 seconds
run 1200000
unfix movecad2
run 100000