Open AccessThe influence of an unstable turbulent wind spectrum on the loads and motions on floating Offshore Wind Turbines
Author(s) -
Jonathan Knight,
Charlotte Obhrai
Publication year - 2019
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/700/1/012005
Subject(s) - turbine , turbulence , tower , environmental science , offshore wind power , marine engineering , meteorology , atmospheric turbulence , wind power , atmospheric sciences , mechanics , physics , engineering , aerospace engineering , structural engineering , electrical engineering
Floating offshore wind turbines (FOWT) are exposed to harsh environmental conditions and often experience unstable atmospheric conditions. Including the effects of atmospheric stability should improve the accuracy of fatigue load calculations, and subsequently, the design of the wind turbine. The current standards recommend two turbulence spectral models that are valid for neutral atmospheric conditions only. The objective of this study is to investigate the influence of Hejstrup’s 1981 Unstable Spectra Model on the loads and motions on a spar and a semi-submersible FOWT. This study focuses on the effect of unstable atmospheric conditions in the free stream wind and does not include the effect of wakes. The most significant differences observed in this study were for the tower top torsion loads, where very unstable conditions gave 47% larger loads than neutral conditions for OC3-Hywind turbine and 30.4% larger for OC4-DeepCwind turbine. Since very unstable conditions corresponded to the highest turbulence intensities and larger turbulent fluctuations, they also resulted in higher fatigue loads. The blade root flap-wise loads were also observed to be higher under unstable conditions compared to neutral conditions, but the differences were smaller with 7.5% for OC3-Hywind and 23% for OC4-DeepCwind.