BARTOL, I.K.*; STEWART, W.J.; Old Dominion University; Old Dominion University: Pulsed jet dynamics of squid during ontogeny

Pulsed jetting is used by squids of remarkably different sizes, from hatchlings that are only a few millimeters in length to adults that may grow as large as 18 meters. Over this wide size range, the physics of fluids plays an important role in the evolution of various jet features that are central to propulsive swimming performance. To understand how fluid mechanical constraints shape swimming strategies, brief squid Lolliguncula brevis of different ontogenetic stages were trained to swim in a water tunnel seeded with light reflective particles. Using a dual pulsed laser with light guide arm and a multi-camera motorized rail system, particle-laden water expelled from the funnel was illuminated and videotaped so that jet features could be measured using digital particle image velocimetry (DPIV). Funnel and mantle kinematics also were recorded. Although swimming behavior was highly variable among squid of different life history stages, smaller squid generally exhibited the highest pulsing rates and shortest relative jet structure lengths. Irrespective of life history stage, jet/funnel angle decreased with increased swimming speed and jet velocities always exceeded swimming speed, with the largest differentials often occurring at low speeds. Vortex ring formation in various stages of development was observed for squid of all sizes. The presence of these jet features, particularly in early life history stages, has significant implications for propulsive efficiency and the physical constraints on pulsed jetting.