Hi,
I was thinking about the packing due to gravity drop in an annular region. I used the pour command and got the particles in to a cylindrical region. But Iam not able to delete atoms in a new small cylindrical region inside the first cylindrical region to create annular region. The input command is like this
### Initialization
# Preliminaries
units si
atom_style sphere
atom_modify map array
boundary f f f
newton off
communicate single vel yes
# Declare domain
region domain block -0.017 0.033 -0.017 0.033 -0.001 0.011 units box
create_box 1 domain
# Neighbor listing
neighbor 0.003 bin
neigh_modify delay 0
### Setup
# Material and interaction properties required
fix m1 all property/global youngsModulus peratomtype 5e6 5e6
fix m2 all property/global poissonsRatio peratomtype 0.31 0.31
fix m3 all property/global coefficientRestitution peratomtypepair 2 0.1 0.1 0.1 0.1
fix m4 all property/global coefficientFriction peratomtypepair 2 0.2 0.2 0.2 0.2
# Gravity
fix grav all gravity 9.81 vector 0.0 0.0 -1.0
region void cylinder z 0. 0. 0.015 0. 0.009 units box
fix ins all pour/legacy 10000 1 12345 &
region void vol 0.5 100 rate 1. diam 10e-06 200e-06
# Define the physics
pair_style gran/hertz/history
pair_coeff * *
### Detailed settings
# Integrator
fix integrate all nve/sphere
# Time step
timestep 0.00000001
# Thermodynamic output settings
thermo_style custom step atoms ke cpu
thermo 10000
thermo_modify norm no lost ignore
# Check time step and initialize dump file
fix ctg all check/timestep/gran 1 0.01 0.01
run 1
unfix ctg
# Create imaging information
dump dmp all custom 10000 Desktop/new6/dump.1 id type type x y z ix iy iz vx vy vz &
fx fy fz omegax omegay omegaz radius
run 50000
unfix ins
run 100000 upto
region delete_region cylinder z 0. 0. 0.006 0. 0.009 units box
delete_atoms region delete_region
What could be my mistake ? Please help.
Regards
Hari
chewnins | Fri, 06/12/2015 - 23:10
What keeps them from falling?
I am not seeing anything that keeps the inserted particles from falling away and not being in the deleted region. Since the boundary is f, there should be no particles in the simulation since there are no walls.
dhari27 | Tue, 06/16/2015 - 09:21
So what should I do to get an
So what should I do to get an annular region with outer dia 0.030 and inner dia 0.012 in the above step?
Is it possible by deleting a second region as provided by "region delete_region" command?
cstoltz | Tue, 06/16/2015 - 14:14
OK, some comments:
OK, some comments:
1) Need to upgrade to the LIGGGHTS 3.x syntax.
2) Recommend updating your particle insertion to more modern methods like insert/rate/region or insert/stream (see below)
3) You're listing material/interaction properties for two different particle types, but you specify a create_box with only 1 particle type.
4) Your timestep is too large - it is running at about 81% of Rayleigh time, which is likely going to lead to instability
5) As the previous post mentions, there aren't any walls or a container of some kind, so the particles will eventually just fall through the bottom surface of your simulation domain and be lost.
Once I fixed the syntax, it ran properly and deleted the core of atoms leaving you with an annular region filled with particles. Note that your deletion region doesn't extend all the way to the bottom of your domain, so a few particles may still be in that central part. Also note that you can get away with the larger timestep for now in that your particles aren't really colliding with anything. When they do, you'll likely start to see problems.
An easier way to do this is to create an annular surface and use the insert/stream command to insert particles based only on the annular region. This avoids having to create a bunch of particles and then deleting some of them. See the LIGGGHTS tutorial from a few years ago for an example of a simulation of a shear cell that includes this type of insertion. You'll need to update some syntax from ver 2.x to 3.x, but the changes are pretty simple.
Regards,
Chris
dhari27 | Tue, 06/16/2015 - 19:25
particle range
I could have used insert stream or insert/rate/region command for the above case but I sticked with pour/legacy because I wanted to have a packing with a range of granular particles i.e from 10 microns to 200 microns. Refering the manual I found range condition for only pour/legacy.
Regards
Hari