Evaluation of different wind fields for the investigation of the dynamic response of offshore wind turbines

Abstract

As the size of offshore wind turbines increases, a realistic representation of the spatiotemporal distribution of the incident wind field becomes crucial for modeling the dynamic response of the turbine. The International Electrotechnical Commission (IEC) standard for wind turbine design recommends two turbulence models for simulations of the incident wind field, the Mann spectral tensor model, and the Kaimal spectral and exponential coherence model. In particular, for floating wind turbines, these standard models are challenged by more sophisticated ones. The characteristics of the wind field depend on the stability conditions of the atmosphere, which neither of the standard turbulence models account for. The spatial and temporal distribution of the turbulence, represented by coherence, is not modeled consistently by the two standard models. In this study, the Mann spectral tensor model and the Kaimal spectral and exponential coherence model are compared with wind fields constructed from offshore measurements and obtained from large‐eddy simulations. Cross sections and durations relevant for offshore wind turbine design are considered. Coherent structures from the different simulators are studied across various stability conditions and wind speeds through coherence and proper orthogonal decomposition mode plots. As expected, the standard models represent neutral stratification better than they do stable and unstable. Depending upon the method used for generating the wind field, significant differences in the spatial and temporal distribution of coherence are found. Consequently, the computed structural design loads on a wind turbine are expected to vary significantly depending upon the employed turbulence model. The knowledge gained in this study will be used in future studies to quantify the effect of various turbulence models on the dynamic response of large offshore wind turbines.

Influence of wakes and atmospheric stability on the floater responses of the Hywind Scotland wind turbines

“…The same turbulence model is in Chougule et al12 extended to include a buoyancy term to account for different atmospheric stability classifications. In Cheynet et al 13 and Nybø et al, 14 wind measurements from the FINO1 platform in the North Sea are used to investigate coherence functions for different atmospheric stratification and the fit of these coherence functions and the point spectra of standard models to measurements, respectively.…”

On Turbulence Models and LiDAR Measurements for Wind Turbine Control

“…However, there are two different turbulence models defined in the IEC standard: the Mann turbulence model and the Kaimal turbulence model. The impact of different wind fields on the dynamic response of an offshore wind turbine has been evaluated by Nybø et al (2020). Held and Mann (2019) extended the previous works by Haizmann et al (2015), Simley et al (2012), andSchlipf et al (2013a) to analyze LiDAR measurement coherence with both the Mann turbulence model and Kaimal turbulence model.…”

“…The symbol denotes the real part of a complex number. Please note that the coherence can be split into a real part and an imaginary part, which are referred to as co-coherence and quad-coherence (Nybø et al, 2020). The coherence expressed in Eq.…”

FAST.Farm load validation for single wake situations at alpha ventus

“…Classification of atmospheric stability with power law exponent α. The given wind field parameters σ k are dependent on stability and based on findings by Peña et al (2010), which is explained in Sect. 2.4.…”

“…The relationship of turbulent fluctuations of the three wind speed components u, v, and w is then adjusted according to atmospheric stability (see Table 1). It is based on findings by Peña et al (2010), who investigated, among other things, the anisotropy of turbulence with respect to atmospheric stability. Their values of the anisotropy parameter are translated to standard deviations by using the relationships provided by Mann (1998).…”