Meeting Abstract
Fish bodies vary widely in shape, from streamlined torpedo-like fish to very flat, almost disc-like shapes, and many variations in between. Their bodies also differ in their internal mechanical properties: some fish have very stiff bodies, while others can be extremely flexible. How do these properties work together to influence the swimming performance of different fish species? A parameter called the “effective flexibility,” which combines length, aspect ratio, stiffness, and bending frequency, has been shown to capture much of the dynamics of thrust production in flexible rectangular panels. It is not known how well it approximates the behavior of more complex bodies like those of fish. I used elastomer models of fish, based on the body shape of the bluegill sunfish (Lepomis macrochirus), to vary shape and material properties separately. I actuated the models using a single sting, rotating back and forth in the pitch axis, and measured thrust, lateral force, and mechanical power requirements. I also quantified the three-dimensional flow patterns behind each model using a TSI V3V volumetric particle image velocimetry system. For all models, all forces increase with increasing frequency. At frequencies that correspond to the same effective flexibility in different shape and stiffness models, the forces have a complex relationship with both shape and stiffness.
