Numerical Analysis of the Effect of Offshore Turbulent Wind Inflow on the Response of a Spar Wind Turbine

Putri, Rieska Mawarni; Obhrai, Charlotte; Jakobsen, Jasna Bogunović; Ong, Muk Chen

doi:10.3390/en13102506

Cited by 11 publications

(14 citation statements)

References 18 publications

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“…Figure 9 shows that low horizontal co-coherence (W5) causes significant M z , while low vertical cocoherence (W4) causes high M T, y . These observations are in agreement with the findings of Putri et al and Doubrawa et al 11,12 A simplified illustration showing the impact of the co-coherence on response is given in Figure 10. 'A' is a simplified version of W5, 'B' of W4 and 'C' of W3, while 'D' shows the situation at higher frequencies.…”

Section: Expected Impact Of Shear Turbulence and Coherencesupporting

confidence: 90%

“…6 For design purposes it is common to assume that if the wind field has a given shear profile and turbulence intensity, the response of the wind turbine is not very dependent upon the spectral and coherence model used. On the contrary, previous studies [7][8][9][10][11][12] have shown that the structural loads in the response of the wind turbine are sensitive to the model chosen.…”

mentioning

confidence: 91%

“…Both the research community (e.g., previous works 7,[11][12][13][14][15] ) and the industry (e.g., previous works 16 ) look for improved turbulence models. They should be valid for large rotors (200 m in diameter) and account for variations in atmospheric stability conditions.…”

mentioning

confidence: 99%

“…The complexity of models are therefore increased and more site parameters are included. Several studies 7,11,12,14,17 group wind fields by stability and evaluate its impact on response. The improved certainties in the response of the offshore wind turbines may still not be worth the additional computational time and/or measurements required.…”

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confidence: 99%

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Quasi‐static response of a bottom‐fixed wind turbine subject to various incident wind fields

2021

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In the design of offshore wind farms the simulated dynamic response of the wind turbine structure includes loading from turbulent wind. The International Electrotechnical Commission (IEC) standard for wind turbine design recommends both the Mann spectral tensor model and the Kaimal spectral model combined with an exponential coherence formulation. These models give deviating wind loads. This study compares these two models to a large eddy simulations model and a model based on offshore wind measurements. The comparisons are performed for three situations, covering unstable, neutral and stable atmospheric conditions. The impact of the differences in the wind fields on the quasi-static response of a large bottom-fixed wind turbine is investigated. The findings are supported by an assessment of the impact of individual wind characteristics on the turbine responses. The wind model based on measurements causes high tower bottom and blade root flapwise bending moments due to a high wind load at very low frequencies. Low and negative horizontal coherence is obtained using the Mann spectral tensor model. This causes relatively large yaw moments as compared to the results using the other wind models. The largest differences in response are seen in the stable situation. We furthermore show that the quasi-static wind load has great impact on the total damage equivalent moments of the structure. From the results, we conclude that in the design of large offshore wind turbines one should carefully consider the structure of the turbulent wind.Further, longer simulations than recommended by the standards should be used to reduce uncertainty in estimated response.

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Section: Expected Impact Of Shear Turbulence and Coherencesupporting

confidence: 90%

mentioning

confidence: 91%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Quasi‐static response of a bottom‐fixed wind turbine subject to various incident wind fields

2021

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“…The characteristics of the MABL differ from the overland atmospheric boundary layer (ABL) due to the larger proportion of the occurrence of non-neutral atmospheric stability conditions than on land (Barthelmie, 1999;Archer et al, 2016). Since the 2010s, several studies have indicated that diabatic wind conditions may significantly affect the fatigue life of offshore wind turbines (OWTs) components (Sathe et al, 2013;Hansen et al, 2014;Holtslag et al, 2016;Doubrawa et al, 2019;Nybø et al, 2020;Putri et al, 2020). Recent measurements from the first commercial floating wind farm (Hywind Scotland) have even shown the direct influence of the atmospheric stability on the floater motion (Jacobsen and Godvik, 2021).…”

Section: Introductionmentioning

confidence: 99%

Turbulence in a coastal environment: the case of Vindeby

Putri

Cheynet

Obhrai

et al. 2021

Preprint

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Abstract. Turbulence spectral characteristics for various atmospheric stratifications are studied using the observations from an offshore mast at Vindeby wind farm. Measurement data at 6 m, 18 m and 45 m above the mean sea level are considered. At the lowest height, the normalized power spectral densities of the velocity components show deviations from Monin-Obukhov similarity theory (MOST). A significant co-coherence at the wave spectral peak frequency between the vertical velocity component and the velocity of the sea surface is observed, but only when the significant wave heights exceed 0.9 m. The turbulence spectra at 18 m generally follow MOST and are consistent with the empirical spectra established on the FINO1 offshore platform from an earlier study. The data at 45 m is associated with a high-frequency measurement noise which limits its analysis to strong wind conditions only. The estimated co-coherence of the along-wind component under near-neutral atmosphere matches remarkably well with those at FINO1. The turbulence characteristics estimated from the present dataset are valuable to better understand the structure of turbulence in the marine atmospheric boundary layer and are relevant for load estimations of offshore wind turbines. Yet, a direct application of the results to other offshore or coastal sites should be exercised with caution, since the dataset is collected in shallow waters and at heights lower than the hub height of the current and the future state-of-the-art offshore wind turbines.

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Sensitivity of the dynamic response of a multimegawatt floating wind turbine to the choice of turbulence model

2022

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In the design of offshore wind turbines, it is important to make a realistic estimate of the wind load. This is particularly important for floating wind turbines, having natural frequencies in a frequency range where the wind loads are high and large turbulent structures exist. This study shows that turbulence modelling greatly impacts the response of a 15-MW floating wind turbine. The turbulence models recommended by the International Electrotechnical Commission (IEC) are challenged by considering two additional models: Large Eddy Simulations (LES) and an approach using input from offshore wind measurements (TIMESR). The two standard models, the Kaimal spectrum with IEC coherence model (Kaimal) and the Mann spectral tensor model (Mann), differ in their coherence formulation. This results in higher standard deviations for the surge and pitch motions, and lower for the yaw motion, when applying Kaimal in comparison to Mann. For the specific floater of this study, more damage is obtained in the mooring lines when applying Kaimal. Applying the more realistic models, LES and TIMESR, increases the range of response further, concluding that the two standard turbulence models may lead to incorrect estimations of the response of a floating wind turbine. LES and TIMESR take atmospheric stability into account, which is proven to alter the response significantly.

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Numerical Analysis of the Effect of Offshore Turbulent Wind Inflow on the Response of a Spar Wind Turbine

Cited by 11 publications

References 18 publications

Quasi‐static response of a bottom‐fixed wind turbine subject to various incident wind fields

Quasi‐static response of a bottom‐fixed wind turbine subject to various incident wind fields

Turbulence in a coastal environment: the case of Vindeby

Sensitivity of the dynamic response of a multimegawatt floating wind turbine to the choice of turbulence model

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