wall particles vibration

Hi all
Im simulating a poiseuille flow and i want to tether the wall molecules via a spring so that I used the fix spring self command
although the spring constant in lj units is 200 but the wall particle move more than a vibration that is expected in a solid wall
any one has an idea how can I fix the problem

Maybe change the spring constant or spring length?


If you use very stiff springs make sure you take care of reducing the
simulation timestep appropriately.
Otherwise your dynamics will be messed up.