Impacts of water depth increase on offshore floating wind turbine dynamics

This paper aims at investigating the effect of water depth increase on the global performance of a floating offshore wind turbine, with a special focus on the environmental loading effects and turbine operating status. An integrated aero-hydro-servo-elastic (AHSE) analysis was simulated in the time domain. The model was first validated against published results in terms of mooring system restoring force and platform natural frequencies. The considered water depth is between 200 and 300 m, which is the deep-water range used in the current floating offshore wind turbine (FOWT) industry. In this study, both normal operating and failure conditions were considered. Key conclusions from case studies indicated that, based on the current water depth range, platform heave motion with slack mooring configurations and mooring line top tension are more sensitive to water depth. Water depth increase influences the tower base bending force when the turbine has a high-speed shaft brake due to grid loss, but the effects are restricted to the high-frequency response range (>2 Hz) and less obvious than the influences on mooring lines.