Figure 3.

Schematic showing the near-field and far-field fluid flow due to whirling cilium motion, modelled as a tilted rotating rod. The near-field is rotational, while the far-field is a ‘stresslet’ straining flow. The leftward movement of the cilium (thick green arrow) causes a long range leftward stresslet flow (thin green arrows), while the rightward movement of the cilium (thick purple arrow) causes a long range rightward stresslet flow (thin purple arrows). Owing to the posterior tilt, the rightward movement occurs closer to the cell surface than the leftward movement, so that the rightward flow velocity is smaller than the leftward flow velocity due to viscous interaction with the surface. Hence, there is an overall leftward flow in the far-field.