Comparing active and passive flexibility in oscillating propulsors

Passively flexible swimmers show increased efficiency over rigid hydrofoils due to resonance. Biological swimmers have been observed controlling the flexibility of their propulsors, presumably to achieve higher thrust and efficiency while swimming. Our goal is to prove there is a theoretical propulsive benefit to active (time dependent) flexibility in basic oscillating propulsion. We introduce active flexibility into previous passive flexibility models through a pseudo spectral method. The fluid is assumed 2 dimensional, inviscid, and the dynamics linearized in small amplitude deflections. Passively and actively flexible flat plates are compared over a wide parameter space of temporal and spatial flexibility distributions. We optimize for thrust and efficiency across the parameter space. By theoretically proving there is a benefit to active flexibility we tie foundational unsteady hydrodynamics to biological observation.