Diffusion of chiral active Brownian particles in oscillatory Poiseuille flow
Micro- and nanoswimmers diffusing in a fluid flow confined to microchannels are often described by overdamped active Brownian particle dynamics, in which viscous effects dominate and inertia is negligible. Here, we investigate the diffusive behavior of chiral self-propelled particles in a two-dimensional microchannel with oscillatory Poiseuille flow. Using numerical simulations, we show that the effective diffusion coefficient strongly depends on the oscillation frequency, flow strength, intrinsic angular velocity, and rotational diffusion rate. Interestingly, the effective diffusion coefficient can oscillate with oscillation frequency and flow strength, exhibiting distinct maxima and minima. The enhanced diffusion peaks arise from resonant diffusion associated with the matching between the flow oscillation time scale and the intrinsic characteristic diffusion time scale. Moreover, we identify an additional vorticity matching mechanism, leading to alternating channel wall accumulation of particles during successive flow half-cycles. Additionally, chiral particles strongly amplify the resonant diffusion, producing diffusion enhancements of several orders of magnitude compared to nonchiral particles. The results of this study could have implications for controlling the diffusion of self-propelled particles in microfluidic channels using time-dependent flow.