cohesion particle wall

Submitted by Frozeus on Fri, 01/19/2018 - 21:07

Hello everyone, I would like to ask for your help in a script that I am working on

It consists of three particles of different sizes but of the same material and a different material geometry.

The problem is that I can not achieve cohesion or adhesion between the particles and the walls but if between the particles

atom_style sphere
atom_modify map array
boundary m m m
newton off

communicate single vel yes
units si
region domain block -0.3 0.3 0.0 0.2 -0.3 0.3 units box
create_box 2 domain
neighbor 0.05 bin
neigh_modify delay 0

#Material properties
fix m1 all property/global youngsModulus peratomtype 5.e6 5.6e6
fix m2 all property/global poissonsRatio peratomtype 0.45 0.45
fix m3 all property/global coefficientRestitution peratomtypepair 2 0.1 0.1 0.1 0.1
fix m4 all property/global coefficientFriction peratomtypepair 2 0.05 0.05 0.05 0.05
fix m5 all property/global cohesionEnergyDensity peratomtypepair 2 300000 30000 30000 30000

#pair style
pair_style gran model hertz tangential history cohesion sjkr #Hertzian with cohesion
pair_coeff * *

timestep 0.00005

#Forces of gravity
fix gravi all gravity 9.81 vector 0.0 0.0 -1.0

#box walls
fix boxwalls_x1 all wall/gran model hertz tangential history primitive type 1 yplane 0.0
fix boxwalls_x2 all wall/gran model hertz tangential history primitive type 1 yplane 0.2

#import mesh from cad:
fix cad1 all mesh/surface file meshes/cilindro.stl type 1
fix bucket_wall all wall/gran model hertz tangential history cohesion sjkr mesh n_meshes 1 meshes cad1
fix inface all mesh/surface file meshes/insertion_face.stl type 1

#distributions for insertion
fix pts1 all particletemplate/sphere 15485863 atom_type 2 density constant 1450 radius constant 0.02
fix pts2 all particletemplate/sphere 15485867 atom_type 2 density constant 1550 radius constant 0.01
fix pts3 all particletemplate/sphere 49979693 atom_type 2 density constant 1650 radius constant 0.005
fix pdd1 all particledistribution/discrete 32452843 3 pts1 0.44 pts2 0.19 pts3 0.37

#Particle instertion
fix ins all insert/stream seed 32452867 distributiontemplate pdd1 &
nparticles 6000 vel constant 0.0 0.0 -1.0 particlerate 1000 overlapcheck &
yes insertion_face inface extrude_length 0.08
fix integr all nve/sphere

#make a dump of particles and the stl file
dump dmp all custom/vtk 200 post/movingMesh_*.vtk id type type x y z ix iy iz vx vy vz fx fy fz omegax omegay omegaz radius
dump dumpstl all mesh/stl 200 post/dump*.stl

#run with particle insertion
run 2000 upto
unfix ins

#run to let particle settle
run 2001 upto

#now lift the particles up
fix rotatecad1 all move/mesh mesh cad1 rotate origin 0. 0. 0. axis 0. 1. 0. period 1.
run 10000

richti83's picture

richti83 | Mon, 01/22/2018 - 19:50

As you didn't provide cilindro.stl I can not test the script but I guess CED 300000 is to low, timestep is to high and period is to fast to get particles "glued" to mesh wall.
From my experience CED depends on PSD as the overlapping area is somewhere in the force formula. (see documention of sjkr(2)). So maybe the g-force is higher than adhesion force ?

I'm not an associate of DCS GmbH and not a core developer of LIGGGHTS®
ResearchGate | Contact

zumack | Thu, 12/20/2018 - 06:58

Why in LIGGGHTS the cohesion density energy is in J/m3. When Johnson-Kendall-Roberts theory say that is the surface energy, and that is in J/m2?. What is the relation betwen both of that definitions?. Because in the literature the definition of the cohesion energy density is other than the adhesion, and that is related with chemestry, it seems here is a mistake in definitions. So, the process to calibrate this values with experimental data is confuse.

Please say to me what paper could I can read for understand the approach did for LIGGGHTS with this terms

Thanks

Frozeus | Tue, 01/23/2018 - 14:16

If the problem was that the adhesion was small.
I will take your other advice into account

Thanks!