Study On The Hydrodynamic Performance Of Semi-submersible Floating Foundation Of Offshore Wind Turbine

Offshore wind turbines develop rapidly in the world for there are many advantages, such asthe stability of the wind energy resource, high wind speed, no pollution and so on. The researchand development of wind power equipment is one of the hottest issues of the engineering andtechnical fields. The wind turbines in deep water always use floating foundation. The research offloating foundation for offshore wind turbines is a widespread concern in the marine engineering.It is of great significance for promoting the progress of offshore wind turbines.This article begins with an overview of the research progress of offshore wind turbines, thenintroduces the theory on the calculation of offshore wind turbines’ environment loads. Based onthe5MW wind turbine of NREL, a type of semi-submersible floating foundation for offshorewind turbine is designed in concept.For the new semi-submersible floating foundation, the static stability is analyzed at thebeginning of this paper. Considering the matrix of viscous damping, the frequency domainanalysis is carried out. The hydrodynamic coefficients and amplitude-frequency response curvesare studied. Based on these, short-term forecast is presented. On the joint action of wind, wave,current, with consideration of the coupling effects of wind turbine and mooring system tofoundation, the time domain analysis is performed for the dynamic response and mooring tensionof floating wind turbine in stochastic wave. For extreme sea conditions, considering theenvironment loads, safety of the mooring system is studied.The main conclusions:First, reduce the center of gravity can effectively improve the initial stability of thefoundation. Reasonable subdivision of the basis can ensure damage stability.Secondly, considering the role of the viscous damping in frequency domain analysis, thecalculation is more accurate. Frequency result shows that mean wave drift and second-orderwave difference frequency force may induce horizontal movement.Third, time domain result shows that the wind turbine can work normally even understate4.And the design of mooring system can meet the requirements in both complete state anddamaged state under extreme sea state. All these show that the design of the floating foundationis reasonable.