68th Annual Meeting of the APS Division of Fluid Dynamics (November 22, 2015 — November 24, 2015)

P0036: Nature-inspired active and passive kinematics of a flapping foil

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Authors

• Junyoung Kim, Pohang University of Science and Technology
• Junshin Park, Pohang University of Science and Technology
• Donghyun You, Pohang University of Science and Technology

DOI: https://doi.org/10.1103/APS.DFD.2015.GFM.P0036

Carangiform locomotion is a mode of swimming that highly laterally compressed fishes use to generate thrust. In carangiform locomotion, a fish flexes only the posterior part of its body to create side to side undulations. The active motion of a tail is often modelled as heaving and pitching motions of a foil and the passive motion of a tail is realized by mimicking the flexibility of a foil in nature.

In order to visualize the flow structure behind a flexible foil, flow visualization experiments were performed in water channel. Heaving and pitching motion of a foil is actuated by using newly designed machine and its dynamic motion is controlled by stepper motors. A modified type NACA0006 foil is used to design a foil and soft material selection with geometrical modification allowed the passive generation of flexible motion during experiment. Dye injection system is integrated with a foil to eject dye from leading edge. The experiments were performed in a dark room to specifically excite the fluorescein dye with UV light.

Time series visualization images are arranged vertically and selected set of images show distinctive structure of leading edge and trailing edge vortices. For a fixed Reynolds number, the results of experiment emphasize the growth in deformation of a foil and secondary vorticity as Strouhal number increase.