Schooling and trajectory deflection of two side-by-side burst-and-coast swimmers at intermediate Reynolds number

This is the authors' abstract. We don't add key points for this paper.

Aquatic animals often utilize intermittent swimming gaits or schooling formations to optimize propulsion and energy efficiency. This study investigates the hydrodynamic interactions and swimming performance of two self-propelled, two-dimensional intermittent swimmers with varying initial configurations. Using computational fluid dynamics based on the immersed boundary method, we systematically examine the effects of initial arrangement and phase difference on collective swimming behavior. The results reveal that synchronized motion with similar amplitudes promotes stable schooling, particularly in a side-by-side configuration. Interestingly, the lateral drift direction of the paired foils during schooling contrasts with that of an isolated foil exhibiting identical kinematics, indicating a fundamental shift in the hydrodynamic interactions. However, collective swimming does not improve propulsion speed or efficiency in intermittent swimmers. Instead, the swimming speed decreases to less than 95% of that of a single foil, accompanied by a slight decrease in efficiency. These findings provide new insights into the hydrodynamics of intermittent locomotion, the limitations of collective swimming, and the tradeoffs between energy efficiency and hydrodynamic interactions in schooling swimmers.