How Dynamic Damping can be Beneifical for Rapid Swimmers

Flexibility plays a crucial role in the dynamics of flapping propulsors. Both biological systems and robot models have demonstrated that by changing the stiffness of a flexible foil state of high thrust generation or efficient swimming can be achieved. Yet, biomimetic robots still cannot achieve the same performance as biological swimmers. Recent biology studies have revealed fish not only tune their body stiffness but also modulate damping during maneuvers. We speculate that this dynamic damping might be related to the rapid swimming capabilities observed in nature. To explore the damping effects and associated wake dynamics, we focus on a prescribed heaving, cyber-physically passive pitching hydrofoil, which can vary its stiffness and damping responses arbitrarily, allowing extensive automatic parametric sweeps. The wake structure is investigated using particle image velocimetry. Combining the two measurement methods, we offered a detailed understanding of the underlying physics of damping effects on swimming for the first time.