Passive particles driven by self-propelled particle: The wake effect

Abstract

This study focused on the numerical exploration of hydrodynamic interactions between a passive particle and a self-propelled particle, termed a squirmer, using a two-dimensional lattice Boltzmann method. We discovered that the squirmer has the capacity to capture a passive particle and propel it simultaneously, provided the passive particle is situated within the squirmer's wake. Our research established that the critical trap distance, which determines whether the particle is captured, primarily depends on the intensity of the squirmer's dipolarity. The stronger dipolarity of squirmer results in an increased critical trap distance. Conversely, the Reynolds number was found to have minimal impact on this interaction. Interestingly, we determined that the passive particle, when driven by the squirmer's wake, contributes to a reduction in the squirmer's drag. This results in a mutual acceleration for both particles. The implications of our findings can provide valuable perspectives for establishing principles to reduce drag in micro-swimmers and assist in achieving the goal of employing micro-swimmers for cargo transport without physical tethering.