Aviscous, incompressible, Newtonian liquid flows in steady, laminar flow down a vertical wall. The thickness, , of

Aviscous, incompressible, Newtonian liquid flows in steady, laminar flow down a vertical wall. The thickness, δ, of the liquid film is constant. Since the liquid free surface is exposed to atmospheric pressure, there is no pressure gradient. For this gravity-driven flow, apply the momentum equation to differential control volume dx dy dz to derive the velocity distribution in the liquid film.