The COTUR project: Remote sensing of offshore turbulence for
wind energy application

Cheynet, Etienne; Flügge, Martin; Reuder, Joachim; Jakobsen, Jasna Bogunović; Heggelund, Yngve; Svardal, Benny; Garfias, Pablo Saavedra; Obhrai, Charlotte; Daniotti, Nicolò; Berge, Jarle; Duscha, Christiane; Wildmann, Norman; Onarheim, Ingrid Husøy; Godvik, Marte

doi:10.5194/amt-2020-511

Cited by 4 publications

(6 citation statements)

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“…by Kristensen and Jensen [25]. The recent COTUR study [24] has attempted to measure co-coherence for lateral separation at different heights at MABL but has not been classified as a function of atmospheric stability. The floater yaw response of a spar WT has been shown to be susceptible to the spatial variation of turbulent wind, particularly in the lateral direction [26], where a lower magnitude of lateral-separation co-coherence may cause a higher platform yaw response.…”

Section: Discussionmentioning

confidence: 99%

Wind-induced response of an offshore wind turbine under non-neutral conditions: A comparison with Hywind Scotland

Putri

Obhrai²

2022

J. Phys.: Conf. Ser.

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In this study, aeroelastic simulations of a 5 MW spar wind turbine are performed by using simulated wind fields that are representative of surface layer marine atmospheric turbulence under different atmospheric stratifications. The spar floater’s motion responses from the simulations are then compared with the observations from Hywind Scotland’s 6 MW spar wind turbine. The platform’s pitch and yaw motions from the simulations are consistent with the observations, in terms of mean wind speed and atmospheric stratification. The simulations and the observations show that a stable atmosphere induces the lowest platform pitch and yaw motions compared to neutral and unstable stratifications. Nonetheless, the discrepancy of platform motions between stable and unstable conditions is more pronounced from the observations than in the simulations. Uncertainties associated with the estimation of the atmospheric stability and the modelling of the turbulence’s co-coherence for lateral separation may partly account for the discrepancies between the observed and the simulated motion responses of the spar wind turbine.

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Section: Discussionmentioning

confidence: 99%

Wind-induced response of an offshore wind turbine under non-neutral conditions: A comparison with Hywind Scotland

Putri

Obhrai²

2022

J. Phys.: Conf. Ser.

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“…GE Renewable Energy, 2021). At such heights, MOST may no longer be applicable (Peña and Gryning, 2008;Cheynet et al, 2021). Above the surface layer, the velocity spectra tend to be invariant with height, which is coarsely accounted for in IEC 61400-1 ( 2005) and suggested by preliminary observations from Doppler wind lidar instruments in coastal areas (Cheynet et al, 2021).…”

Section: Co-coherence Of Turbulencementioning

confidence: 99%

“…Further studies are, however, needed to better quantify this possible overestimation since the lateral co-coherence is also required but could not be obtained at FINO1 nor SMW. The co-coherence for lateral separations may be obtained using Doppler wind lidar instruments (Cheynet et al, 2016(Cheynet et al, , 2021 or wind sensors mounted on unmanned aerial vehicles (Wetz et al, 2021;Vasiljević et al, 2020) since deploying multiple masts at offshore is likely too costly.…”

Section: Co-coherence Of Turbulencementioning

confidence: 99%

“…At such heights, MOST may no longer be applicable (Peña and Gryning, 2008;Cheynet et al, 2021). Above the surface layer, the velocity spectra tend to be invariant with height, which is coarsely accounted for in IEC 61400-1 ( 2005) and suggested by preliminary observations from Doppler wind lidar instruments in coastal areas (Cheynet et al, 2021). Højstrup (1982) proposed an empirical turbulence spectral model for a convective boundary layer up to 0.5z i , where z i is the convective boundary layer height (Wyngaard and Coté, 1972), that could be used to characterize turbulence above the surface layer.…”

Section: Co-coherence Of Turbulencementioning

confidence: 99%

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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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“…Further, the COTUR project studies the offshore turbulence with remote sensing techniques (Cheynet et al 2021) Additionally, the approximation of coherence with different approaches is examined. The results are discussed in Sect.…”

Section: Introductionmentioning

confidence: 99%

Analyses of Spatial Correlation and Coherence in ABL flow with a Fleet of UAS

Wetz

Zink

Bange

et al. 2022

Preprint

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The spatial structures of turbulent flow in the atmospheric boundary layer (ABL) are complex and diverse. Multi-point spatial correlation measurements can be used to improve the understanding of these structures and their statistics. In this context, we investigate Taylor’s hypothesis and the statistics of spatial structures on the microscale in this study. For the first time, simultaneous horizontally distributed wind measurements with a fleet of 20 quadrotor UAS (unmanned aerial systems) are enabled. The measurements were taken at different heights and under different atmospheric conditions at the boundary layer field site in Falkenberg of the German National Meteorological Service (DWD). An adaptable horizontal flight pattern has been especially developed, consisting of measurements distributed along and lateral to the mean flow direction with separation distances of 5...205 m. The validity of Taylor's hypothesis is studied by examining cross-correlations of longitudinally distributed UAS and comparing them with autocorrelations of single UAS. To assess the similarity of flow structures on different scales, the lateral and longitudinal coherence of the streamwise velocity component is examined. Two modeling approaches for the decay of coherence are compared. The experimental results are in good agreement with the model approaches for neutral atmospheric conditions, whereas in stable and convective ABL, the exponential approaches are not unconditionally valid. The validation results and the agreement with the literature on coherence in the ABL underline the potential of the UAS fleet for the purpose of spatial turbulence measurements.

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The COTUR project: Remote sensing of offshore turbulence for wind energy application

Cited by 4 publications

References 58 publications

Wind-induced response of an offshore wind turbine under non-neutral conditions: A comparison with Hywind Scotland

Wind-induced response of an offshore wind turbine under non-neutral conditions: A comparison with Hywind Scotland

Turbulence in a coastal environment: the case of Vindeby

Analyses of Spatial Correlation and Coherence in ABL flow with a Fleet of UAS

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