Hello,
Please find my code below. I am simulating a problem in which particles are allowed to enter in a column and then of the column's gate is removed to create a flow. I am losing atoms after certain trials of insertions. This is reflected in the post processing (Paraview) as particles vanish from the column during insertion.
#Simple granular column collapse
atom_style granular
atom_modify map array
boundary f f f
newton off
communicate single vel yes
processors * * *
units si
region reg block -0.01 0.35 -0.01 0.1 -0.01 0.15 units box
create_box 2 reg
neighbor 0.0021 bin
neigh_modify delay 0
#Material properties required for new pair styles
fix m1 all property/global youngsModulus peratomtype 5.e6 1.e9
fix m2 all property/global poissonsRatio peratomtype 0.31 0.3
fix m3 all property/global coefficientRestitution peratomtypepair 2 0.3 0.3 0.3 0.3
fix m4 all property/global coefficientFriction peratomtypepair 2 0.7 0.7 0.7 0.8
#New pair style
pair_style gran model hertz tangential history #Hertzian without cohesion
pair_coeff * *
timestep 0.0001
fix gravi all gravity 9.81 vector 0.0 0.0 -1.0
#the gccm
fix surface1 all wall/gran model hertz tangential history primitive type 2 zplane 0.0
fix wall1 all wall/gran model hertz tangential history primitive type 2 yplane 0.0
fix wall2 all wall/gran model hertz tangential history primitive type 2 yplane 0.09
fix wall3 all wall/gran model hertz tangential history primitive type 2 xplane 0.0
fix wall4 all wall/gran model hertz tangential history primitive type 2 xplane 0.05
#distributions for insertion
fix pts1 all particletemplate/sphere 15485863 atom_type 1 density constant 1450 radius constant 0.0021
fix pdd1 all particledistribution/discrete 32452843 1 pts1 1.0
#region and insertion
region column block 0. 0.05 0. 0.09 0. 0.05 units box
#particle insertion with porosity 0.26
fix ins all insert/rate/region seed 67867967 distributiontemplate pdd1 &
mass 0.24 massrate 4.8e-2 insert_every 1000 overlapcheck yes all_in yes vel constant 0. 0. -1.0 &
region column ntry_mc 10000
#apply nve integration to all particles that are inserted as single particles
fix integr all nve/sphere
#output settings, include total thermal energy
compute 1 all erotate/sphere
compute 2 all ke/atom
compute 3 all pe/atom
compute 4 all erotate/sphere/atom
compute 5 all coord/atom 0.0021 mix no
thermo_style custom step atoms ke c_1 vol
thermo 1000
thermo_modify lost ignore norm no
#insert the first particles so that dump is not empty
run 1
dump dmp all custom 300 post_2/dump*.shi_2 id type type x y z ix iy iz vx vy vz fx fy fz omegax omegay omegaz radius c_2 c_3 c_4 c_5
#insert particles
run 55000 upto
unfix wall4
run 100000
Kindly help me with this issue.
Thanks.
Aman.
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mschramm | Mon, 01/17/2022 - 19:55
Time step too large
Hello,
your time step is >50% Rayleigh time. I lowered your timestep by a factor of 10 and the issue is gone.
Also,
after your run 55000 upto command
you will want to unfix ins as well otherwise you will continue to add particles as the atoms leave the box.
Aman | Thu, 01/20/2022 - 04:48
Coordination Number not showing correct
Hi mschramm,
Thank you very much for your quick help. Reducing the time step really fixed the problem.
But now I have another issue. I am not getting correct values of coordination number and energy per atom.
Kindly help me with this as early as possible.
Thanks.
Aman.
Aman | Wed, 01/19/2022 - 13:39
Coordination Number not showing correct
Hello mschramm,
Thank you very much for such a quick help. It worked well. But I am facing one more problem. The values of coordination number and energy values per atom is not correct. It is showing a very very less value.
Kindly see the above code once more and help me with this problem as well.
Thanks.
Aman.