FIG. 3.

Geometry of particle capture in the Kuwabara flow field. Lighter (darker) shading corresponds to faster (slower) flow speed. (a) Diagram of limiting trajectory: the particle path which only just collides with the fiber. In the absence of attractive forces and inertia the capture angle will be ${\theta }_1=\pi /2$. (b) and (c) Effect of spherically symmetric forces on the incoming particle trajectories. The forces move the limiting trajectory toward the near or far side of the fiber depending on whether the interaction is attractive (b) or repulsive (c). (d) and (e) Inertia brings the limiting trajectories toward the near side of the collecting fiber, shown are particle trajectories for (d) $\text{St}=0$ and (e) $\text{St}=0.5$.