velocity profile for couette flow

will do, thanks for letting me know. All lammps users, I would appreciate any suggestions and help I can get. I am trying to get the velocity profile for couette flow using about 10000 particles. I am having difficulties, particles are not moving like they’re supposed to, see below.

Thank you,
Haz

particles are not moving like they’re supposed to, see below.

Simulations of flows are a rather standard topic in Molecular Dynamics. The
early book by Allen and Tildesley
https://global.oup.com/academic/product/computer-simulation-of-liquids-9780198556459?cc=be&lang=en&
already reviews them.

What can help?

1. Making a schematic of your simulations.
2. Desin a flowchart of the simulations, including the sampling of the
quantities that interest you.
3. Make sure that you simulation script makes sense with respect to the above.

To proceed, several points are important:
1. Do not neglect any warning or error message output by LAMMPS
2. Analyze your data to assign a physical meaning to "not moving like they're
supposed to"
3. Use the existing literature, tutorials and posts on this mailing list to make
sure that your problem was not already solved.

It is only by showing that you have considered the advice given and by
explaining your issues clearly that other will be able to give you meaningful
help.

Regards,

Pierre

Dear all,

The quantities I am interested in are the velocities. Now I tried the compute chunk/atom command and fix ave/chunk to get the velocity profile, I get the error Invalid compute style. I followed the description for compute chunk/atom command and these are the lines I wrote

compute 1 all chunk/atom type

fix 1 all ave/chunk 10 1 10 1 vx vy file velprofile

Why is the style invalid? chunk/atom is one the styles for compute command

Thank you Pierre for your help and recommending that book, the book is very helpful for my research.

Best Regards,
Haz

Dear all,

The quantities I am interested in are the velocities. Now I tried the
compute chunk/atom command and fix ave/chunk to get the velocity profile, I
get the error Invalid compute style. I followed the description for compute
chunk/atom command and these are the lines I wrote

compute 1 all chunk/atom type
fix 1 all ave/chunk 10 1 10 1 vx vy file velprofile

nope. that is not it. there is an example for computing a velocity
profile in the current documentation for fix ave/chunk. RTFM!

Why is the style invalid? chunk/atom is one the styles for compute command

that would happen, if you use an outdated version of LAMMPS, our have
non-ASCII characters in your input file.

axel.