Abstract
Numerical experiments on the interaction of self-driven particles in a fluid have been conducted in order to understand the collective motion of animal aggregates (flocks of birds, schools of fishes, etc.). In the model, a vortex-pair particle with a fixed center distance as the fluidic auto-propulsive particle (Flapper) was introduced. We analyzed the interaction between two Flappers in two spatial dimensions, and showed their fundamental behavior such as attractive and repulsive motions. Their behavior depends on the relative position and orientation between them because the hydrodynamic effect by the fluid flow around the objects plays an important role in their interaction process. We also examined the collective motion of 1000 Flappers hovering in a gravity field. The aggregation of Flappers maintains its shape (or formation) and position by incorporating a simple protocol to control the motion of each Flapper like animal' s taxis, while the aggregation collapses and diffuses without the protocol.
