A preliminary investigation of caudal fin shape effects on thrust and power of a newly designed robotic tuna

Thunniform swimmers are known to travel at high speeds for long periods of time and at high hydrodynamic efficiency. Thus, there is a great deal of interest in their swimming physics. In order to better understand these physics, a newly designed robotic tuna was constructed that allows for interchangeable caudal fins. This robot was put in a water tunnel and tested at tail beat frequencies ranging from 0.5 to 1.0 Hz and at freestreams of 0, 0.2, and 0.4 m/s. A lever assembly was used to transmit thrust force to a load cell, and power was calculated using data from current sensors. Preliminary results suggest that swept caudal fins produce more thrust and are more efficient than trapezoidal fins at higher freestreams while the opposite is true at lower freestreams. However, several induction factors need to be resolved before more confident assertions can be made.