Drag on a plane beneath a translating cylinder
= Drag on a plane beneath a translating cylinder
{title2=$F_x=2\pi\mu U\sqrt{2a/h_0}$}
For a full Newtonian liquid film in the <lubrication approximation>, a cylinder translating parallel to a stationary plane with minimum gap $h_0\ll a$ exerts tangential force $2\pi\mu U\sqrt{2a/h_0}$ per unit axial length on the plane. The leading normal force vanishes by the odd symmetry of excess <pressure>.