Fig. 2.

Inertial focusing leads to a consistent direction in the particle-induced convection. Both direction and intensity of the particle-induced net secondary flow depend on the lateral position of the drag- and torque-free particle. Even when the particle is at the channel center (completely symmetric conditions, therefore not rotating) there exists a set of net secondary flows in the channel (case i), which are nearly two orders of magnitude weaker than the normal case (i.e., inertially focused particle, case iv). When the particle is located off-center, the magnitude of the secondary flows increases (case ii), however, as the particle reaches its equilibrium position the secondary flow changes direction (compare cases iii and iv). Therefore, inertial focusing of the particle determines the lateral distance of the particle from the channel center (Δy), defining the direction of the secondary flow in experimental systems.