Effects of strong turbulence structure coherent on load of blade root in a yaw wind turbine

Abstract: The strong turbulent wind has a significant impact on the dynamic load of wind turbine blade in a yaw state. Because the root of blade is the most stressed position, the dynamic characteristics of load are the key factors affecting the life and safe operation of wind turbine. In this study, the NWTCUP (The NREL National Wind Technology Center Model) wind spectrum model was used to couple KHB (Kelvin-Helmholtz Billow) flow, in order to construct a strong turbulent coherent structure wind condition. Subsequently, the FAST (Fatigue, Aerodynamics, Structures, and Turbulence) program was used to calculate the aerodynamic load of the NREL 1.5MW wind turbine under different yaw angles. Finally, the effect of KHB turbulent coherent structure was investigated on the dynamic load of wind turbine blade roots under yaw conditions. The results showed that the turbulent coherent structures increased the amplitude and energy of load fluctuations in a wind turbine. The increase of yaw angle has a smaller effect on the blade root edgewise moment, while a greater effect on the blade root flapwise moment, indicating the stronger dispersion of both factors. The turbulent coherent structure reduced the average value of blade root edgewise moment by 1.903%, while increased the average value of blade root flapwise moment by 2.906%. In Wavelet analysis of the root load, the turbulent coherent structure has a small effect on the energy of the edgewise moment, while, the energy was mainly concentrated in the low frequency band, corresponding to u'w', v'w'. There was a significant effect in terms of the leaf root flapwise moment, where the energy change corresponds well with u'w'. The energy of leaf root flapwise moment increased, as the yaw angle increased.