velocity plot from lammps output file

Hi Team,

I was trying to get velocity profile from 2D Poiseulle flow.
I added

dump 5 all custom 500 velocities1.txt type x y vx vy

and created velocity of atoms as per attached dump.
How to get velocity profile from the dump ?
I understand create_box within the region , is it possible to get velocities from it with some modification ? or do we need to use some other tool with lammps output file ?

velocities1.txt (301 KB)

in.flow.poisV1 (1.64 KB)

See ‘in.nemd.2d’ file in the /examples/VISCOSITY in your lammps distribution.

These 2 commands produce a velocity profile. See the fix ave/chunk documentation http://lammps.sandia.gov/doc/fix_ave_chunk.html to see how to specify how the velocity profile is averaged.

compute layers all chunk/atom bin/1d y center 0.05 units reduced
fix 4 all ave/chunk 20 250 5000 layers vx file profile.nemd.2d

HI Vanessa / Lammps User,

I run the code adding the velocity average lines . But I’m getting below errors :

LAMMPS (26 Jan 2017-ICMS)
OMP_NUM_THREADS environment is not set. Defaulting to 1 thread. (…/comm.cpp:90)
using 1 OpenMP thread(s) per MPI task
Lattice spacing in x,y,z = 1.28436 2.22457 1.28436
Created orthogonal box = (0 0 -0.321089) to (25.6871 22.2457 0.321089)
1 by 1 by 1 MPI processor grid
Created 420 atoms
60 atoms in group lower
60 atoms in group upper
120 atoms in group boundary
300 atoms in group flow
Setting atom values …
60 settings made for type
Setting atom values …
60 settings made for type
ERROR: Replacing a fix, but new style != old style (…/modify.cpp:798)
Last command: fix 4 all ave/chunk 20 250 5000 layers vx file profile.nemd.2d

in.flow.poisV1 (1.79 KB)

It is solved . Need to change the fix ID.

Thanks
Sisir