Underwater Biomimetic Propulsion Using Coupled Structures

The flapping motion of caudal fin found in fishes like Mackerel, salmon and trout has been extensively studied for its excellent propulsion characteristics. Locomotion is generally achieved through the oscillatory motion of the peduncle and a caudal fin at the end. In the current work, the two body parts are modelled as Euler–Bernoulli beams with appropriate stiffeners at their joint. The fluid domain surrounding the structure is modelled using potential flow theory. The fluid-structure interaction results in an added-mass effect, which significantly impacts the thrust generated. The mean thrust is correlated to the tip velocity of the structure and hence it could be maximised by increasing the bandwidth of peak response. A parametric analysis is carried out to identify the sensitive range of the stiffness parameters. The results indicate that by proper tuning of the coupling between the peduncle and the attached fin, the thrust output can be controlled.