Figure 3.

Force on the disc due to Π-dependent η_s as a function of distance from the plane wall, following equations (3.6) and (3.12). This $\mathcal{O}(\zeta )$ force acts perpendicular to the wall and breaks the kinematic reversibility of Stokes flow. The dashed line is the ϵ^−5/2 behaviour predicted by the lubrication analysis (§3c).