Shear-induced bimodality and stability analysis of chiral spheroidal swimmers (2302.08483v1)

Abstract: We study the shear-induced behavior of chiral (circle-swimming) and nonchiral swimmers in a planar channel subjected to Poiseuille (pressure-driven) flow. The swimmers are modeled as active Brownian spheroids, self-propelling with a fixed-magnitude velocity, pointing along their axis of symmetry. We consider both cases of prolate and oblate swimmers and focus primarily on swimmers that possess an intrinsic, or active, counterclockwise angular velocity, in addition to the shear-induced angular velocity they acquire within the channel flow (Jeffery orbits). The probabilistic results are established using a Smoluchowski equation within the position orientation phase space that is solved numerically. We show that the interplay between shear- and chirality-induced angular velocities, combined with the effects due to particle self-propulsion and steric particle-wall interactions, lead to an interesting range of effects, including pinning, off-centered and near-wall accumulation of swimmers within the channel. This is further accompanied by the linear stability analysis of swimmers, used to explain the probabilistic results. We discuss the qualitative differences of probabilistic results that emerge due to the different regimes of rotational dynamics of swimmers in channel flow, particularly the shear-trapping/-escaping of prolate/oblate swimmers and the difference in latitudes of fixed points associated with each swimmer shape. Our results point to possible mechanisms for flow-driven separation of active spheroidal particles based on their chirality strength.