[lammps-users] How to calculate the driving Pressure in Poiseuille flow in a channel

Hi everyone,

I am simulating pressure driven Poiseuille flow of water with two walls in z- direction. And I use fix addforce in x direction to simulate that there is a pressure drop in x direction, which can drive the water flow along x direction. Here is my question; I want to know the pressure drop when I simply add a force on each water molecule. For sure there are a lot ways to calculate the pressure of the system and printed out, but I just wander how to get the driven pressure drop, or can I simply take the pressure differences of the system between before add force and after add force?

Thank you! Have a nice day!


Back of the envelope, I think it is just pressure = force/area
and you are applying a per-atom force which corresponds to
a force density, which you can convert to force/area at the
ends of the box (yz area).