Figure 8.

Streamlines corresponding to a disc (a) translating and (b) rotating in an unbounded Newtonian monolayer. (c) Surface pressure contours due to translation (rotation does not alter the surface pressure). Darker shades correspond to a relative increase in Π ahead of the disc. The associated increase in η_s leads to the $\mathcal{O}(\zeta )$ force F^⊥ that ‘rolls’ the disc in a direction perpendicular to U, leading to a curved trajectory. (Online version in colour.)