Experimental and numerical analysis of wind field effects on the dynamic responses of the 10 MW SPIC floating wind turbine concept

Experimental methods are useful to study global responses of floating wind turbines under wind excitations. One experimental technique is based on the regeneration of wind fields in open space in a hydrodynamic laboratory and the use of the performance-matched rotor to produce the equivalent aerodynamic thrust force according to a target wind field. However, for wind generation systems, due to small variations in the output of each fan and differences among the fans, the obtained wind speed varies in space and time, making it difficult to generate the target ideal uniform, constant or time-varying wind fields. For investigating the quality of the wind field in the experiment and their effects on the global responses, numerical simulations under wind only conditions for the full-scale 10 MW SPIC wind turbine were compared with the upscaled responses from model tests. Because of the limitation in the generation and measurement of the target wind field, and the model scaling issue for wind turbine aerodynamics considering the TSR variation, there are uncertainties in interpreting the obtained responses. Numerical simulations were then performed to investigate the effects of spatial and temporal variations in wind fields. Wind shear influences 1P and 3P responses. Below the rated wind speed, when the turbulence intensity increases, the average responses decrease and the response spectra are dominated by low-frequency and 3P components. In Kaimal and Mann wind fields with coherent structures, the generated power and pitch motion show fewer fluctuations than in uniform time-varying wind field, while the nonuniform wind field excites greater 1P and 3P responses.