Meeting Abstract
Turning manuevers comprise a large portion of aquatic animal swimming performance, yet little is known about turning hydrodynamics of many swimmers, including squid, which employ a dual mode propulsive system involving flexible, paired fins and a pulsed jet that can be directed within a hemisphere below the body. While 2D velocimetry approaches are useful for examining the individual contribution of either a fin or the jet, 3D velocimetry approaches, such as defocusing digital particle tracking velocimetry (DDPTV), provide more complete information about how the jet and fin components work together to accomplish turning maneuvers. Multi-camera high-speed videography and DDPTV were used to collect kinematic and hydrodynamic data of brief squid Lolliguncula brevis during turns. Matlab code was used to analyze body kinematics and calculate impulse and angular impulse for the fins and jet. Several broad turning categories were identified, including wide sweeping turns, tail-first and arms-first sharp turns, and vertically oriented turns. While flow patterns and impulse magnitude varied among the categories, the jet generally created larger impulses than the fins during turns. Fin flows were complex with both isolated vortex rings and regions of elongated tubular vorticity being observed. One common pattern involved one fin acting as a brake while the other fin flapped/undulated to produce propulsive flows. Interactions between jet and fin vorticity were also commonly observed. This study demonstrates that both the fins and jet play important roles in turning and that 3D approaches can provide important insights into turning performance.
