Stability of Passive Locomotion in Periodically-Generated Vortex Wakes
The passive locomotion of a body placed in a thrust wake is examined. This work is motivated by a common belief that live and inanimate objects may extract energy from unsteady flows for locomotory advantages. We propose idealized wake models using periodically-generated point vortices to emulate shedding of vortices from an un-modeled moving (thrust) object. We investigate the two-way coupled dynamics of a submerged rigid body with such thrust wakes. In particular, we seek and obtain periodic trajectories where a circular body ‘swims’ passively against the flow of a thrust wake by extracting energy from the ambient vortices. These periodic trajectories are unstable, as indicated by the associated Floquet multipliers. The instabilities are particularly strong for elliptic bodies where rotational effects are at play.
Key wordsBody-vortex interactions passive locomotion stability
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