Experimental and numerical study of a barge-type floating offshore wind turbine under a mooring line failure

Abstract

This study investigated the transient response due to a mooring line failure on a barge-type floating offshore wind turbine (FOWT). A 1/64 scale model of the FOWT with eight catenary mooring lines was installed in a wave tank to be separately subjected to wind, wave, and current loads. An electromagnet attached to the fairlead of the FOWT was used to disconnect the mooring lines. First, free decay test was performed to ensure the suitability of the scaled model. Then, the individual contributions of wind, wave, and current loads were compared based on the 50-year return period to investigate their influences on the movement of the FOWT after failure. The results showed that the wave effect was the most important factor, followed by current and wind. Then, the mooring loads and rigid body motions of the FOWT under mooring line failure in wind, current, and wave conditions were investigated. Finally, two commercial codes (ANSYS AQWA and OrcaFlex) were used to compare the experimental results in waves. The comparison findings showed that the potential flow-based numerical model overestimates the dynamic response. This result implies the significant damping effect of the barge-type FOWT.