Study on the motion of squirmers close to a curved boundary

We numerically investigate the behaviors of a hydrodynamic squirmer interacting with a circular obstacle using the lattice Boltzmann method. It is interesting to find that in most cases, pullers (gaining thrust from the front) move forward while pushers (gaining thrust from the rear) move backward. We describe six swimming patterns of the squirmer: orbiting forward, ∞-loop, dancing forward, C-loop, orbiting backward, and scattering; notably, three of these have not been previously reported. The association between pressure and viscous stress can reasonably explain the movement of the squirmer near the obstacle. In certain modes, squirmers can swim faster near obstacles. The swimming Reynolds number Res and dipolarity β have significant effects on the averaged velocity and Strouhal number of the swimming patterns. A stronger polarity encourages the squirmers to swim faster and “bounce” more often.