Swimming dynamics of a spheroidal microswimmer near a wall

In this work, we investigate the swimming dynamics of a spheroidal squirmer near a flat wall for various aspect ratios using the direct-forcing fictitious domain method. Our results show that the swimming mode of a strong pusher undergoes the transition from either oscillating or escaping to crawling as the aspect ratio increases. A strong puller exhibits an opposite transition: from crawling to escaping and then to oscillating as the aspect ratio increases. The mechanism for the near-wall swimming behavior of a strong puller and pusher is explored by analyzing the hydrodynamic force and torque on a swimmer with its height and orientation fixed. The results indicate that both collision and hydrodynamic toques are important to the near-wall swimming state of the squirmer. Additionally, we found that the initial orientation angle and the release distance do not influence the swimming mode when the squirmer initially swims toward the wall at an angle smaller than -π/8.