Hydrodynamics of tandem flapping pectoral fins with varying stroke phase offsets

Low-speed maneuvering and station keeping capabilities for small unmanned underwater vehicles (UUVs) are of great interest to the maritime community and flapping fins provide a potential solution for achieving these capabilities. We show how phasing between tandem bio-inspired fins flapping at high stroke amplitudes, i.e. by leading or lagging the rear fin with respect to the front fin modulates its thrust production, leading-edge suction and the overall wake characteristics of the system using load cell thrust measurements, two-dimensional particle image velocimetry measurements and three-dimensional computational fluid dynamics simulations.