Modeling the hydrodynamic interaction of two chiral organisms

The hydrodynamic interaction between two chiral organisms (chirality parameter 0 ≤ C2 ≤ 10) swimming toward each other is investigated using the lattice Boltzmann method over a Reynolds number range of 0.01 ≤ Re ≤ 5, with the swimming parameter β = ±5. Our findings reveal that in a finite inertial flow regime, with a low C2 for chiral squirmers, enhancing the C2 leads to a strengthened attraction between pullers (a type of squirmer) and other chiral squirmers. Simultaneously, this strengthening reduces the repulsive tendencies observed in pushers (another type of squirmer). Beyond a certain threshold (C2 ≥ 5), an increase in the C2 causes the flow field generated by a pusher to resemble that of a puller, there by initiating an attractive influence on another squirmer. At this point, with an increase in C2, the mutual attraction between pullers and pushers intensifies. Moreover, as the C2 continues to increase, the duration of the intense interaction between colliding pullers or pushers steadily diminishes, contrasting with the increased duration of the intense interaction between non-colliding pushers. These empirical insights substantively enhance our comprehension and empirical investigation of collective behavioral dynamics in chiral microorganisms.