Characteristics of a fish aggregating device with ocean energy harvester

Abstract

Fishes are easy to be gathered around fish aggregating devices (FADs), which is an environment-friendly artificial ocean infrastructure. This study has proposed and developed a new type of FAD with a current turbine to generate an independent electric power for navigational and environmental sensors, especially at archipelago areas with fishery and aquaculture. A mooring type of FAD with a horizontal axis turbine (HAT) or a vertical axis turbine (VAT) was designed to avoid an unexpected collision with fishes. The characteristics of fluid force on FAD were investigated by numerical and theoretical works assuming steady state in time and the motions of FAD were also examined by experimental works. The proposed FAD can achieve 15% reduction for averaged snap load and 30% for maximum one. The amplitudes of surge, sway and heave motions excited by vortex-induced vibration (VIV) in wave-current conditions can be reduced up to 50%. The current flow around FAD and designed turbine was computed by CFD to estimate hydrodynamic force and vortex field. The numerical results in the fluid force are in overall agreement with the experimental and theoretical ones. Moreover, generated electric power by the optimized turbine was estimated at a typical archipelago area in Indonesia. The first model of FAD without turbine was built up and has been installed in real ocean field.