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lammps/examples/VISCOSITY/in.wall.2d
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in.wall.2d
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# sample LAMMPS input script for viscosity of 2d LJ liquid
# use shearing wall, thermostat via fix langevin
# settings
variable x equal 20
variable y equal 20
variable ylo equal -2.5
variable yhi equal 23
variable rho equal 0.6
variable t equal 1.0
variable rc equal 2.5
variable srate equal 2.7
# problem setup
units lj
dimension 2
atom_style atomic
neigh_modify delay 0 every 1
lattice sq2 ${rho}
region simbox block 0 $x ${ylo} ${yhi} -0.1 0.1
create_box 3 simbox
create_atoms 1 box
mass * 1.0
pair_style lj/cut ${rc}
pair_coeff * * 1 1
region lower block INF INF INF 0.0 INF INF
region upper block INF INF $y INF INF INF
group lower region lower
group upper region upper
set group lower type 2
set group upper type 3
group wall union lower upper
group flow subtract all wall
velocity flow create $t 97287
velocity upper set ${srate} 0.0 0.0 units box
compute thermal flow temp/partial 0 1 0
compute flow flow temp
fix 1 all nve
fix 2 flow langevin $t $t 0.1 498094
fix_modify 2 temp thermal
fix 3 wall setforce 0.0 0.0 0.0
fix 4 flow ave/spatial 20 500 10000 y center 0.05 vx &
units reduced file profile.wall.2d
fix 5 all enforce2d
# equilibration run
variable ybox equal $y*ylat
compute tilt flow temp/ramp vx 0 ${srate} y 0 ${ybox} units box
thermo 1000
thermo_style custom step temp c_tilt epair etotal press pxy
run 20000
# data gathering run
variable visc equal -pxy/(v_srate/ly)
fix vave all ave/time 1000 1 1000 v_visc ave running
thermo_style custom step temp pxy v_visc f_vave
thermo_modify temp tilt
# only need to run for 5000 steps to make a good 100-frame movie
#dump 1 all custom 50 dump.wall.2d id type x y z vx
#dump 2 all image 50 image.*.jpg vx type zoom 1.6 adiam 1.2
#dump_modify 2 pad 5 amap 0.0 ${srate} ca 0.0 2 min blue max red
run 50000
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