Dear all,
I am new to LAMMPS ,when I begin to learn it ,I try to duplicate the work of others to understand the command ,
when I run the Sample from 《Numerical Simulation of Viscous Flow: A Study of Molecular Dynamics and Computational Fluid Dynamics 》by Jeremy Fried , I have some problems:
I use the fix ave/spatial command to get velocity and density information .but the velocity distribution looks higher and the density distribution looks lower than Jeremy’s work as we have the same input file. what wrong ?
Best regards,
here is the velocity distribution: Graph_ux.jpg
and the velocity distribution from Jeremy :Jeremy.jpg
the input file:
3D Poiseuille Flow
dimension 3
boundary p p p
atom_style atomic
neighbor 0.3 bin
neigh_modify delay 5
geometry
lattice fcc 0.45
region box block 0 10.0 -10.0 7.5 0 10.0 units box
create_box 2 box
create atomic lattices
mass 1 1.0
mass 2 1.0
region 1 block INF INF -10.0 -7.5 INF INF units box
region 20 block INF INF -10.0 -9.16667 INF INF units box
region 21 block INF INF -9.16667 -8.33333 INF INF units box
region 22 block INF INF -8.33333 -7.5 INF INF units box
region 2 intersect 2 1 box side out units box
create_atoms 1 region 2
lattice none
lattice fcc 0.85
create_atoms 2 region 1
group wall region 1
group first region 20
group second region 21
group third region 22
group flow subtract all wall
potential calculation
pair_style lj/cut 1.12246
pair_coeff * * 1.0 1.0 1.12246
initial velocities
compute mobile flow temp
compute stationary wall temp
fix 1 all nve
Poiseuille flow
minimize 1.0e-3 1.0e-5 100 1000
fix 2 flow addforce 0.1 0.0 0.0
wall
fix 7 wall temp/rescale 1 0.722 0.722 0.0001 1.0
fix 5 wall spring/self 57.1
fix 20 first recenter NULL INIT NULL
fix 21 second recenter NULL INIT NULL
fix 22 third recenter NULL INIT NULL
run
timestep 0.0001
thermo 1000
thermo_modify temp mobile
dump 1 flow custom 2500000 dump2.flow y vx
dump 2 all atom 50000 flow2.lammpstrj
fix ans flow ave/spatial 2 5000 5000000 y center 0.1 y vx density/number file fix2.dat
run 10000000
