Experimental measurement of the wake of a oscillating fish body model

Over eons of evolution, fish have evolved the innate ability to manipulate the fluid in their wake to facilitate their locomotion. The organization of the fluid in the wake consists of chains of vortex rings produced by a single flapping fin, which has previously been described using particle imaging velocimetry (PIV) water tunnel experiments. The goal of this study is to create a passively flexible fish model with nineteen rigid rib components that can pivot relative to each other. Using 20 3D printed body sections, brass pins, a laser cut caudal fin, a modified camshaft, and monofilament, the model is able to execute a simple traveling wave motion. In future versions of this model, the fish will be able to execute prescribed realistic movement as actuation will be based on the angle of turn and radii of the camshaft. This design allows for the wakes across a range of Strouhal numbers and caudal fin models to be visualized through PIV. The model approximates the natural movement of a fish without compromising the ability to collect consistent and reliable data.