This work is dedicated to comparing the experimental and numerical results of the dynamic responses of a novel floating system integrating a floating offshore wind turbine with a steel fish farming cage (FOWT-SFFC) under wind and wave loadings. The patents of this floating system have been successfully licensed recently in China and USA.
The experimental study is carried out in the Ocean Basin of Tsinghua Shenzhen International Graduate School, with a Froude scaling of 1:30. A small commercial wind turbine is used to produce the scaled wind loads on FOWT-SFFC in terms of the similarity of thrust force.
In this paper, the setup of model tests is described first. Second, a numerical model of prototype FOWT-SFFC is built in the software OrcaFlex. Then, this numerical model is calibrated and updated by the results of free decay tests and static offset tests in the basin. The numerical model also adopts three sets of drag coefficients. Finally, the experimental results of FOWT-SFFC under a variety of load cases are presented and compared with the numerical simulation results. They include seakeeping tests for hydrodynamic motion response amplitude operators (RAOs) and dynamic responses corresponding to normal operating and survival conditions. The numerical simulation results show that, though they are in good agreement with model test data especially on time records of dynamic responses, they are sensitive to the selection of drag coefficients particularly on extreme values and low-frequency spectral contents. Appropriate drag coefficients are suggested to be used in the numerical model for a specific environmental condition. Drag coefficients benchmarked from the free decay tests may not be suitable for moderate and harsh wave conditions.