Dynamic Analysis of a Novel Floating Wind Turbine and Fish Cage Combined System

In recent years, the combined floating offshore wind turbine and fish cage has garnered significant attention as a novel form of clean energy infrastructure. In this study, a novel combined floating offshore wind turbine and fish cage structure was proposed. A three-dimensional diffraction/radiation analysis was performed in the frequency-domain using the WADAM program to compute hydrodynamic coefficients, such as added mass, radiation damping, first-order wave exciting forces, wave drift force coefficients, and motion. Additionally, second-order difference-frequency wave forces were calculated using the Newman approximation method. Time domain analysis was carried out using ORCAFLEX. The results of frequency domain analysis, including hydrodynamic coefficients (potential added mass and damping), transfer functions of the 1st and 2nd order wave loads. were substituted into the time domain model. In the ORCAFLEX program, full coupled motion analysis was conducted for wind-wave-current operation and extreme environmental conditions of the combined system. For the wind loads, a decoupled analysis method was applied, with the wind turbine tower base loads as input loads for the lower floating foundation. The analysis also included an assessment of the global motion, accelerations, and heel angles for the semi-submersible platform. The results indicate that the floating offshore wind turbine meets the requirements with a maximum inclination of less than 9 deg under extreme conditions, the maximum inclination in the operation condition meets the requirement less than 5 deg. the maximum acceleration in the extreme condition meets the requirement less than 0.6 g. The maximum acceleration in the operation condition meets the requirement less than 0.3 g. There is no green water phenomenon on the floating wind turbine system. The novel combined system exhibits favorable motion performance and can serve as a reference for engineering practice.