Noise-Induced Aggregation of Swimmers in the Kolmogorov Flow

We investigate a model for the dynamics of ellipsoidal microswimmers in an externally imposed, laminar Kolmogorov flow. Through phase-space analysis without noise, we find that swimmers favor either cross-stream or rotational drift, depending on their swimming speed and aspect ratio. When including i.e., diffusion, are driven into certain parts phase space, leading to nonuniform steady-state distribution. This distribution exhibits transition from swimmer aggregation low-shear regions flow high-shear as swimmer’s speed, ratio, diffusivity varied. To explain swimmers, apply weak-noise averaging principle produces reduced description stochastic dynamics. Using this technique, trajectories more favorable than others presence weak diffusion. By combining information with along each trajectory, predict space where tend accumulate. The results technique good agreement direct calculations distributions swimmers. In particular, our explains aggregation.