[lammps-users] Some questions of Couette flow

In the example, Couette and Poiseuille flow, the boundaries are the same type and size of atom. Are there any ways that modify the boundary atoms without using the �read_data� command? Furthermore, can we put the boundary that is composed of solid, instead atoms?

You can put the boundary atoms in a group, then use the
set command to change their type. Their type is used in
the LJ potentials to set their size (sigma).

If you want a solid wall, how would it exert drag on the atoms?
You'd have to code some formula for that in a new fix you