Investigating Coherent Structures in the Standard Turbulence Models using Proper Orthogonal Decomposition

The Science of Making Torque from Wind

Eliassen, Lene^1 ; Andersen, Søren^2

Department of Marine Technology, NTNU, Norway^1

Department of Wind Energy, DTU, Denmark^2

关键词: Coherence function;    Coherent structure;    Fatigue life estimates;    Longitudinal components;    Lower frequencies;    Offshore floating wind turbines;    Proper orthogonal decompositions;    Turbine designs;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/753/3/032040/pdf
DOI  :  10.1088/1742-6596/753/3/032040

来源: IOP

【 摘 要 】

The wind turbine design standards recommend two different methods to generate turbulent wind for design load analysis, the Kaimal spectra combined with an exponential coherence function and the Mann turbulence model. The two turbulence models can give very different estimates of fatigue life, especially for offshore floating wind turbines. In this study the spatial distributions of the two turbulence models are investigated using Proper Orthogonal Decomposition, which is used to characterize large coherent structures. The main focus has been on the structures that contain the most energy, which are the lowest POD modes. The Mann turbulence model generates coherent structures that stretches in the horizontal direction for the longitudinal component, while the structures found in the Kaimal model are more random in their shape. These differences in the coherent structures at lower frequencies for the two turbulence models can be the reason for differences in fatigue life estimates for wind turbines.