shear flow

Hi all

I want to model shear flow between two walls using Lammps
I am not getting how to give fixed velocity as well as harmonic motion (with spring constant as input) to the group of atoms that I am using as wall.
Wall atoms are just vibrating about their mean position (which is varying because of fixed velocity). There is no spring force between wall-fluid particles, only LJ potential on fluid because of the wall particles. No other potential between wall-wall particles, the only force is because of the spring.

Thanks in advance

You should be able to formulate your model
using 2 kinds of wall atoms. One set of atoms
that is a perfect wall and moves with a constant
velocity and does not interact with the fluid,
The other set which is bound by a harmonic bond
to each fixed atom, and which does interact
with the fluid, but not (necessarily) with each other.

See the bond_style harmonic command and define
your bonds in the input data file.