One layer of particles sticks on the surface while discharging from an orrifice

Submitted by Zeynep on Mon, 07/27/2020 - 15:27

Hello,

I am working on discharging particles from a flat bottom hopper with an orifice. But even I keep particle frictions low one layer of particles seems to stick to the wall surface of the hopper. Even if I reduce time step and increase Young's modulus the result is the same.

Can someone please help me about that?

Here is my input script:

atom_style granular
boundary f f f
newton off
atom_modify map array
communicate single vel yes
units si #(meters, seconds, kg)
timestep 0.00001
processors * * *

#MAKE REGION
region reg block -0.03 0.03 -0.03 0.03 -0.04 0.15 units box
create_box 2 reg
neighbor 1e-3 bin #(in meters)
neigh_modify delay 0

#INTEGRATION
fix 1 all nve/sphere

#MATERIAL PROPS

fix m1 all property/global youngsModulus peratomtype 5e6 5e6
fix m2 all property/global poissonsRatio peratomtype 0.3 0.3
fix m3 all property/global coefficientRestitution peratomtypepair 2 0.5 0.7 0.7 0.7
fix m4 all property/global coefficientFriction peratomtypepair 2 0.1 0.45 0.45 0.1
fix m5 all property/global coefficientRollingFriction peratomtypepair 2 0.1 0.15 0.15 0.1

#FORCE PAIR

pair_style gran model hertz tangential history rolling_friction epsd2

pair_coeff * *

# MAKE GRANULAR WALL

fix cad1 all mesh/surface file mesh/15_mm_orif2.stl type 2 scale 0.001 move 0 0 -0.03
fix cylinder all wall/gran model hertz tangential history rolling_friction epsd2 primitive type 2 zcylinder 0.025 0 0
fix granwalls all wall/gran model hertz tangential history rolling_friction epsd2 mesh n_meshes 1 meshes cad1

#STOPPER
fix stopper_wall all wall/gran model hertz tangential history rolling_friction epsd2 primitive type 2 zplane -.03

#GROUND
#fix ground all wall/gran model hertz tangential history rolling_friction epsd2 primitive type 2 zplane -.07

#PARTICLE INSERTION
fix pts1 all particletemplate/sphere 15485863 atom_type 1 density constant 2554 radius constant 1e-3
fix pdd1 all particledistribution/discrete 15485867 1 pts1 1.0

#REGION OF INSERTION (BOX OLARAK INSERT ET!)
#Cylinder arguments: dim c1 c2 radius lo hi
region factory cylinder z 0 0 0.023 -0.028 0.1 units box

fix ins all insert/rate/region seed 123457 distributiontemplate pdd1 mass 0.15 massrate 10 insert_every 1000 overlapcheck yes region factory ntry_mc 1000

fix ts all check/timestep/gran 1000 0.2 0.1

#INSERT THE FIRST PARTICLES SO THAT DUMP IS NOT EMPTY
run 1

#OUTPUTS
thermo_style custom step atoms ke cpu time
thermo 1000
dump velocity all custom/vtk 1000 post/dump*.vtk id type type x y z vx vy vz omegax omegay omegaz
dump dmpstl all stl 1000 dump_geometry/dump_geometry*.stl

#RUN TO FILL THE HOPPER
run 1000 upto
unfix ins

fix 2 all gravity 9.81 vector 0.0 0.0 -1.0

run 30000 upto

unfix stopper_wall

#RUN TO DİSCHARGE THE HOPPER
run 90000000

AttachmentSize
Image icon weird_result.jpeg77.88 KB
Microsoft Office document icon hopper.doc31.5 KB