Dynamic analysis of an integrated offshore structure comprising a jacket-supported offshore wind turbine and aquaculture steel cage

Abstract

A novel integrated offshore design, JOWT-SC, which combines a jacket-supported offshore wind turbine structure (JOWT) with an aquaculture steel cage (SC), is proposed in this paper. The enclosed steel cage in the integrated design can adjust to changes in water depth, preventing the fish from escaping. The jacket structure is equipped with two decks and a 10 MW reference wind turbine that provide steady electricity for the offshore fish farm. The numerical modeling and time-domain simulations were conducted in software SACS, and the dynamic responses of the JOWT-SC were also compared with the baseline JOWT, that is without a steel cage. The considered environmental conditions include waves measured from the southeast open sea area of Fujian in China, several wind speeds that represent normal operating conditions for the reference wind turbine, and a constant current flow. The results of the study demonstrate that the aquaculture steel cage significantly influences the dynamic responses of the integrated JOWT-SC substructure, and the pile-foundation shear responses are more sensitive to the wave frequency. In particular, the cage increases the hydrodynamic responses of the JOWT-SC at the mudline under the combined action of winds, waves, and currents, compared with the case where the JOWT-SC is only subjected to wind loads. Overall, the results of this study can be used as a reference for the realization of novel designs in practical engineering.