Low Cycle Fatigue Analysis of Offshore Wind Turbines Subjected to Hurricane

The main objective of this paper is to investigate the effects of hurricanes on low cycle fatigue of tower and blades in offshore wind turbines. For this purpose, first, recent observations on hurricane turbulence models were discussed. Second, the buffeting wind loads on the wind turbine structure were introduced. A new formulation was used to address unsteady wind forces on the tower. This new formulation was later used to modify NREL-FAST (Fatigue, Aerodynamics, Structures, and Turbulence) for the analysis. In the next step, according to importance of recent findings about hurricanes, hurricane wind and wave fields were simulated based on the Saffir-Simpson hurricane wind scale. Then, to investigate the effects of various turbulence models on the wind turbine structures, the modified NREL-FAST was used to analyze structure-wind-wave-soil interaction of the NREL-5 MW monopile wind turbine. Finally, the low cycle fatigue analysis was presented and discussed. Results for various hurricane turbulence models showed that by using quasi-steady analysis of the tower, the spectrum Model A and Model B resulted in average 53% lower and 12% higher damage index compared to the conventional Kaimal spectrum model respectively; however, by considering unsteady formulation on the tower, spectrum Model A and Model B resulted in average 96% and 24% lower blade root damage indices compared to the conventional Kaimal spectrum model respectively.