41.3 Saturday, Jan. 5 Performance of Thunniform Propulsion: A High Bio-fidelity Experimental Study DELEPINE, M.B.*; BARANNYK, O.L.; SHADWICK, R.E.; Univ. of British Columbia, Vancouver; Univ. of Victoria, BC; Univ. of British Columbia, Vancouver email@example.com
Tunas, lamnid sharks and whales are some of the fastest sustained swimming animals. These animals are part of the thunniform propulsion (TP) group, characterized by streamlined bodies with narrow necking of the caudal peduncle and high aspect ratio lunate tail that generates lift-based thrust. For these unique reasons, TP has received considerable attention from biologists and engineers. TP is assumed to have the highest propulsive performance (PP) of all swimming modes, meaning high propulsive efficiency at fast swimming speeds. However there is no direct empirical evidence to support this common idea, due to the difficulty of obtaining force measurements for these animals. Consequently, indirect approaches are used, such as theoretical and experimental studies. But these experiments oversimplify the animal (motion, shape or material property) and/or the flow condition. Our goal was to assess the PP of the Atlantic bluefin tuna, Thunnus thynnus, which is our case study for TP, by an experimental approach of the current highest bio-fidelity. A computed tomography scanner and a polyjetTM 3D printer were used to make two tail models: one with materials of similar properties than the in vivo measurements and a rigid one. Each model was actuated in a water tunnel by a computer controlled, motorized system to follow motion paths typical for a tuna. Propulsive efficiencies and thrust coefficients were calculated from the forces and torque measurement for each motion regime. Vortex shedding was visualized by means of digital particle image velocimetry. In conclusion, the PP of other animals and propellers were compared with our results, and major parameters responsible for this enhanced performance were identified.