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[lammps-users] couette flow with walls at different temperatures
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[lammps-users] couette flow with walls at different temperatures


From: m n <mnnfean@...16...>
Date: Fri, 14 Jul 2017 21:46:05 +0000 (UTC)

Dear all,
I want to modify the couette flow input code. I need to specify a low temperature (T=1) for the lower wall and a high temperature (T=2) for the upper wall and find the temperature distribution in the middle flow area. 
The problem is the results are not reasonable since the temperature of the lower wall is "0" in the output file. Could any body help me figure out where the bugs are? 

Thank you so much in advance.
Best, 

Santiago

My modified code is as follows: 

# 2-d LJ flow simulation
 
units lj
dimension 2
boundary p p p

atom_style atomic
neighbor 0.3 bin
neigh_modify delay 5

# create geometry

lattice hex 0.7
region mybox block 0 20 0 10 -0.25 0.25
create_box 3 mybox
create_atoms 1 box

mass 1 1.0
mass 2 1.0
mass 3 1.0

# LJ potentials

pair_style lj/cut 1.12246
pair_coeff * * 1.0 1.0 1.12246

##########
velocity        all create 1.0 23652 mom yes rot yes
fix             npt all npt temp 1 1 0.01 iso 0 0 0.1
##########

# define groups

##########
unfix           npt
##########

region        1 block INF INF INF 1.25 INF INF
group        lower region 1
region        2 block INF INF 8.75 INF INF INF
group        upper region 2
group        boundary union lower upper
group        flow subtract all boundary

set        group lower type 2
set        group upper type 3

# Couette flow

velocity        lower set 0.0 0.0 0.0
velocity        upper set 3.0 0.0 0.0
fix        1 boundary setforce 0.0 0.0 0.0
fix        2 all enforce2d

########## HOT & COLD
fix 3 lower nvt temp 1 1 0.01            
fix 4 upper nvt temp 2 2 0.01
fix 5 flow nve
##########  
compute         hot upper temp
compute         middle flow temp   
compute         cold lower temp
##########
fix             6 all ave/time 1 10000 10000  c_hot c_middle c_cold  file temp.txt

# Run

timestep 0.003
thermo 500
dump 1 all xyz 100 dump.xyz
dump 2 all movie 100 movie.mpg type type &
zoom 1.6 adiam 1.2
run 50000