Meeting Abstract

3.6  Friday, Jan. 4  Flow patterns associated with swimming motions of benthic and pelagic batoids as visualized with DPIV FISH, F E*; NEAL, D; FONTANELLA, J E; DINENNO, N; GABLER, M K; West Chester Univ., Pennsylvania; LaVision, Michigan; West Chester Univ., Pennsylvania; West Chester Univ., Pennsylvania; West Chester Univ., Pennsylvania ffish@wcupa.edu

Batoid fishes display undulatory and oscillatory swimming kinematics of the enlarged pectoral fins that are associated with either benthic or pelagic habits, respectively. Each swimming mode is related to distinct flow patterns that are linked to the propulsive efficiency of the fin motion. Digital particle image velocimetry (DPIV) was used for quantitative flow visualization. Batoids were tested in a long still water tank, where the ray could dictate its own swimming speed, or in a flow tank at 0.25 m/s. The wake structures were visualized for the undulatory Atlantic stingray (Dasyatis sabina) and freshwater ray (Potamotrygon motoro) and the oscillatory cownose ray (Rhinoptera bonasus). The wake of the rays was characterized by vortices shed from the trailing edge of the pectoral fin with a posteriorly oriented momentum jet flow. For undulating rays swimming along the bottom of the tank, the momentum jet was horizontally directed, whereas when swimming in the water column, the jet was directed at a downward angle to the horizontal. The cownose ray produced a wake with a thrust-type vortex street of two staggered rows of alternating vortices that were generated from the distal end of the pectoral fin. The cambered profile of the rigid central body induced water movement in the wake with a downward directed component. The fluid motion and vorticity in the wake of swimming batoids show distinct differences in pattern that are associated with thrust production for each swimming mode, buoyancy control and with proximity to the bottom.