Dynamic Motion Analysis of Catenary Moored Spar Wind Turbine in Extreme Environmental Condition

摘要

Survivability is an important design aspect of all types of structures, also floating wind turbines which are subjected to dynamic response due to stochastic wave and wind loads Wind turbines should be designed for different conditions such as Operational and Survival conditions. In high sea states the response can be quite different from operational condition. The present paper deals with coupled wave and wind induced motions in harsh condition up to 15 (m) significant wave height and 50 (m/sec) average wind speed The deep draft of spar platforms makes it necessary to consider the instantaneous position for calculating wave forces. This instantaneous position adds some nonlinearity to the equation of motions. It is found that nonlinear dynamic effects have more effects around natural frequencies and less effect in wave frequency part. In harsh conditions the coupled dynamic response is dominated by wind induced response. The dynamic response of the rigid and elastic floating wind turbine (FWT) in harsh condition is found to be almost the same. A comparison between constant and turbulent wind showed that the constant wind excites the pitch natural frequency and the turbulent wind excites both low frequency (surge natural frequency) and pitch natural frequency (the pitch resonance response due to steady wind load is dominant). No instability problem was found in the current analysis. As the aerodynamic damping in a parked turbine is less than for an operating turbine, introduction of more hydrodynamic damping can decrease the pitch resonant response.