Problem with fix deform

Thank you for your reply, Steve.
I’m wondering if there is another way to obtain a linear velocity profile.
Can I use “velocity ramp”? I’ve tried this command, but it doesn’t work.
The code is like:
velocity ar ramp vx -5.0 5.0 y -53 53 units box sum yes

Why does it matter? Axel.

I think Axel’s right but I do happen to use two oppositely moving walls (instead of deforming) and velocity ramp to create a linear velocity profile.

  • Oscar

Either procedure is equivalent because it all boils down to the
relative character of the frame of reference (Galilean relativity in
introductory physics). Lammps implicitly locates the origin at one of
the box edges while the plot you want has it at the center of the box.
The system properties MUST be independent of your frame of reference.