Hydrodynamic behavior of inertial elongated microswimmers in a horizontal channel

In the current study, the lattice Boltzmann method was used to explore the motion of an elongated microswimmer in a horizontal channel with finite fluid inertia. By employing an extended squirmer rod model, the swimming velocity, hydrodynamic efficiency, and interaction with the channel wall of the capsule-shaped squirmer rod were simulated. It was found that the aspect ratio α and the swimming Reynolds number Re_s of the squirmer rod significantly affect its swimming velocity and efficiency. Specifically, as the Reynolds number increases, the pusher rod's velocity increases, whereas the puller rod's velocity decreases. Moreover, compared with the puller rod, the pusher rod has a higher efficiency with the same power consumption. With the increase of the aspect ratio α, the velocity of the squirmer rod increases gradually, the power consumption of the pusher rod and the puller rod decreases gradually, and the efficiency increases gradually, showing the characteristics of lower energy consumption and higher efficiency. During the interaction of the squirmer rod with the wall, four distinct motion modes were identified, namely, steady linear motion, motion away from the wall, damped swinging motion, and wall-attraction oscillation. The emergence of these motion modes and their transitions could be associated with the pressure distribution formed between the squirmer rod and the wall. The results provide another perspective and theoretical basis for the design of bioinspired microswimming devices and microrobots, especially in medical applications such as precision drug delivery systems.