Study On Fluid Dynamic Performance Of A Floating System With Multiple Wind Turbines

Wind energy is of significant developing potential as it's renewable and convenient to use.Compared with onshore wind resource,offshore wind resource is much richer and more pollution-free,which is gradually becoming an international research focus.Under complex ocean environment,intense aerodynamic loads caused by the operating wind turbine bring difficulties to the design and fluid dynamic performance analysis of floating wind turbine platform.Since the coupled dynamic issues of offshore multiple wind turbine system are more complex than that of offshore single wind turbine system,there is still no consensus and comprehensive demonstration on topics like the aerodynamic performance of turbine unit,fluid dynamic loads and motion response of the system.Under this background,this thesis focuses on the wake effects on aerodynamic performance of turbines and configuration of floating platform and mooring system,and the coupled motion responses in time domain under different environment conditions.In respect of turbine unit aerodynamics,the following aspects have been accomplished.First of all,coordinate system of the turbine system is established.Based on the BEM theory and modified method,the aerodynamic computational calculation model of single turbine is established and validated in terms of accuracy.Secondly,the aerodynamic computational calculation model of turbine unit under steady wind is established on the integration of BEM theory and improved Jensen wake model.Through the calculation model,the arrangement scheme of turbine unit is determined and the research on how aerodynamic performance is affected by wake effect under steady wind is conducted.Thirdly,the aerodynamic loads of turbine unit under turbulent wind by using eddy viscosity model of upstream turbine wake,and the research on how aerodynamic performance is affected by wake effect is conducted.Also,the influences of wake effect on aerodynamic performance under different wind environment are summarized.In terms of system research,the configuration of floating platform and mooring system is accomplished on the basis of the fixed turbine unit arrangement.Then,the time-domain computational calculation model of the floating multiple wind turbine system is established by secondary development of AQWA.By using this calculation model,the safety verification of mooring system is conducted.In terms of system motion responses,coupled motion responses of floating multiple wind turbine system is analyzed through the time-domain model established above.The system motion responses under different wind environment are calculated.Then,how steady wind,regular wave and current affect the motion of system is discussed.Besides,analysis on the system motion response under turbulent wind and random wave condition is conducted.Finally,the influences of aerodynamic loads and wind,wave,and current environment on system motion are summarized.