Meeting Abstract
Squid use an integrated fin/jet system powered by muscular hydrostats to swim. The fins are capable of diverse movements with high degrees of freedom and provide propulsive and control benefits that complement the vectored jet system. The complex fluid-structure interactions associated with the fins pose unique challenges for researchers, particularly during turning maneuvers when the fins are especially active. To better understand fin movements and flow generation during turns, we used proper orthogonal decomposition (POD) and defocusing digital particle tracking velocimetry (DDPTV) to study the brief squid Lolliguncula brevis; and the longfin squid Doryteuthis pealeii; as they performed maneuvers in a viewing chamber. Both flap and wave components were present in all fin motions, but the relative importance of the wave components changed with swimming orientation and turning behavior. Fin wave components were generally more prominent during arms-first turns and during controlled tight turns. While a diversity of fin wake patterns was observed, the most complex fin wakes with interconnected vortex structures correlated most closely with fin movements with significant undulatory characteristics. Our results demonstrate that fin motions are diverse and an integral complement to the jet during turning behaviors and our integrative POD/DDPTV approach can be a powerful tool for decoupling fin motions and understanding their momentum consequences.
