[lammps-users] bottom wall motion

Dear Steve, Axel and Others,
I have spent couples of days to script an input-file in which bottom wall of cylinder moves downward or upward with constant velocity. I put all particles in cylinder and after packing I applied shears but wall of cylinder could be moved up or down or it could be rotated along its z-axis. Instead, I want to move the base plane while keeping the cylindrical wall fix. I used many tricks but all in vain. For example,the cylinder was filled from Z-position to the up; the lower portion was empty so that packing could move till origin with constant velocity. there was thin layer of particles at the bottom of packing which prevented the particles to move down. Please anybody have idea of such problems? I would be very thankful.
Sincerely yours,

I'm not clear what you're asking. If you want to move a collection
of particles with a constant velocity, then there are several ways
to do it. E.g. set their initial velocity, turn off the force on them,
integrate them with fix nve.


Actually I want to move bottom(base) of cylinder along z-axis either up or down so that whole packed particles in the cylinder can move up/down with base, the cylindrical wall remains stationary. It is just like moving wall.

The cylindrical wall has nothing to do with the base of particles and
their movement. My previous answer is correct, so far as I can see.