A Performance Analysis of a Flapping-Foil Hydrokinetic Turbine Mimicking a Four-Limb Swimming Creature

Flapping-foil hydrokinetic turbines (FHTs), unlike rotary turbines, are inspired by nature and have recently been presented in various tandem forms. In this study, a tandem hydrokinetic turbine with four hydrofoils that mimics a quadrupedal underwater animal and its movements is developed, with each hydrofoil moving in phase and out of phase, and the performance in terms of the power and load is compared and analyzed. As a result of optimizing the flapping frequency and separation distance, the out-of-phase condition showed superior characteristics in terms of power, with similar efficiency and lower fluctuation levels compared to the in-phase condition. In terms of the load on the body, the force levels in the out-of-phase movement were kept lower than those of the in-phase condition, which is advantageous for the design of the structure supporting the turbine. Therefore, the FHT proposed in this study can utilize more than three hydrofoils, similar to a typical rotary turbine, and can improve the FHT performance by adjusting the phase between the hydrofoils.