Power and load analysis of a flapping-foil hydrokinetic turbine inspired by a four-limb swimming creature*

Among hydrokinetic turbines, which can be used for extracting renewable energy from water flow, a nature-inspired flapping hydrofoil turbine (FHT) becomes highly spotlighted in recent years due to its eco-friendliness, dense arrangement and possibility of installation at shallow water. Very recently, a new flapping hydrofoil turbine have been developed by mimicking a turtle such as the flapping trajectory, flipper’s shape and the front-rear limb configuration etc. In this study, power and load analysis on a tandem FHT by computational fluid dynamic simulations were conducted. The analysis sets were derived for the simulation based on optimal global phase and reduced frequency range.

In the power analysis, efficiency and fluctuation were considered when the phases between front and rear foil were categorized into in-phase and out-of-phase. It is found from the analysis that the out-of-phase had the effect of reducing fluctuation while keeping efficiency a t a similar level compared to the in-phase in the provided analysis sets. In load analysis, phases between left and right foils were also considered and it was recognized that the out-of-phase could reduce the load upon the turbine’s body into under a half compared to the in-phase.

The results of power and load analysis will be utilized in stage of the design for the turtle-mimicking hydrokinetic turbine, and a corresponding prototype will be verified through experiments in a circulated water channel.