Impact of atmospheric stability on wind turbine wake evolution

Subramanian, Balaji; Chokani, Ndaona; Abhari, Reza S.

doi:10.1016/j.jweia.2018.03.014

Cited by 14 publications

(13 citation statements)

References 14 publications

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“…Abkar and Porté-Agel [42] discussed th of atmospheric stratifications on the mean velocity deficit distribution, turbulence statist meandering intensity in the wake region, but the interaction between the wake and atmosphe structures and the main cause of wake meandering were not mentioned. Some recent field [43,44] provided valuable wake information under various atmospheric conditions, but d features such as meandering spectrum and wake structure evolution were not available du limitation of the measurement equipment. One of the primary tasks at present for the wind energy community is to realize the control of overall wind farm performance [45], and this is challenged by the complexity of b dynamic wake itself and its interaction with various ambient conditions [46].…”

Section: Governing Equationsmentioning

confidence: 99%

“…Abkar and Porté-Agel of atmospheric stratifications on the mean velocity deficit distribution, tu meandering intensity in the wake region, but the interaction between the wa structures and the main cause of wake meandering were not mentioned. S [43,44] provided valuable wake information under various atmospheric c features such as meandering spectrum and wake structure evolution were limitation of the measurement equipment. One of the primary tasks at present for the wind energy community control of overall wind farm performance [45], and this is challenged by th dynamic wake itself and its interaction with various ambient conditio circumstance, the present work aims to analyze and characterize wake dyn data gained from simulations, explain the mechanism behind the wake mea atmospheric stabilities, and identify the spectra and magnitudes of main str this phenomenon.…”

Section: Governing Equationsmentioning

confidence: 99%

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LES Study of Wake Meandering in Different Atmospheric Stabilities and Its Effects on Wind Turbine Aerodynamics

Wan

2019

Sustainability

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Wake meandering disturbs the stability of the far wake field and thus increases the fatigue loads of downstream wind turbines. A deep understanding of this phenomenon under atmospheric boundary layers and its relation to the structural loads helps to better model the dynamic wake and alleviate adverse effects. A large eddy simulation and an actuator line model are introduced in the present work to simulate the wake field and aerodynamic loads of wind turbines with different longitudinal spacings. By temporal filtering and the gaussian fitting method, the wake center and edge are precisely defined, and the dynamic wake characteristics, including the wake width, oscillation amplitude, and frequency, are described based on the statistical data of the simulated flow field. Results reveal that the wake meandering is caused by both large-scale atmospheric structure and the unstable vortex shed from the rotor because two distinct meandering frequency ranges are detected. As the atmosphere instability increases, the former becomes the dominant inducing factor of the meandering movements. Further, the analysis of the correlation between the inflow characteristics and the wake deflection shows that the Taylor hypothesis remains valid within a distance of over a thousand meters under both neutral and convective boundary layers, proving the feasibility of using this hypothesis for wake evolution prediction. In addition, our study shows that the fluctuation of blade root moment and yaw moment is significantly intensified by the meandering wake, with their standard deviation is augmenting by over two times under both atmospheric conditions. The power spectrum illustrates that the component with rotor rotation frequency of the former is sensible to the wake effect, but for the latter, the power spectrum density of all frequencies is increased under the meandering wake. These indicate that the fatigue loads will be underestimated without considering the wake meandering effect. Moreover, the high correlation between the wake deflection and yaw moment implies that we can predict yaw moment based on the incoming flow information with high accuracy.

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Section: Governing Equationsmentioning

confidence: 99%

Section: Governing Equationsmentioning

confidence: 99%

LES Study of Wake Meandering in Different Atmospheric Stabilities and Its Effects on Wind Turbine Aerodynamics

Wan

2019

Sustainability

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“…Although the present LES evaluates the geometrical parameters in a narrow range, the trends of the key parameters in the flow interactions between the wind turbine and the hill are clear. The stratification condition 61,62 and the hill slope, 63 which play important roles in flow interactions, are not considered in this study and should be examined in the near future. Conditions under which the superposition method can be adopted should be further verified by observation of real wind farms in complex terrain.…”

Section: Discussionmentioning

confidence: 99%

Large eddy simulations of wind turbine wakes in typical complex topographies

Liu

Ishihara

2020

Wind Energy

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There is a need to clarify the coupling characteristics of terrain-induced wind fields and wind turbine-induced wake in wind farm micrositing. However, research investigating the effect of hill shape on this interaction is lacking. In addition, during the optimization of the layout of the turbines over topographies, the flow behind the turbines should be predicted in a fast way. After obtaining the wake flow of the turbine mounted on flat terrain and the flow over the topographies, there are mainly two superposition methods to predict the turbine wake flow over the topographies.One is to add the wind deficit following the location with a vertical distance of the hub height (D-line). The other is to add the wind deficit following the streamline starting from the turbine center (B-line). It remains unknown to what extent these two superposition methods can be adopted. Therefore, the effects of hill shape, wind turbine size, and turbine location are investigated. When the wind deficit, obtained from modeling the wake flow of the turbine mounted on flat terrain, is superposed following B-line, the results are overall better than those when following D-line.

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“…For instance, information to accurately quantify the implementation of a control strategy is imperative to attributing the resulting variations in wake structure to the control change itself. Given wind turbine wake structure is also sensitive to the underlying atmospheric conditions and inflow variability (e.g., Barthelmie et al, 2013;Machefaux et al, 2016;Lee and Lundquist, 2017;Subramanian et al, 2018), atmospheric conditions must also be simultaneously well documented and understood. To highlight wake sensitivity to atmospheric stability, and to determine how atmospheric stability impacts wind plant control efforts, onshore wake evolution within the early-evening transition (EET) was also investigated using a single-Doppler (SD) data collection approach.…”

Section: Introductionmentioning

confidence: 99%

Exploring the complexities associated with full-scale wind plant wake mitigation control experiments

Hirth

Schroeder

2020

Wind Energ. Sci.

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Recent research promotes implementing next-generation wind plant control methods to mitigate turbine-to-turbine wake effects. Numerical simulation and wind tunnel experiments have previously demonstrated the potential benefit of wind plant control for wind plant optimization, but full-scale validation of the wake-mitigating control strategies remains limited. As part of this study, the yaw and blade pitch of a utilityscale wind turbine were strategically modified for a limited time period to examine wind turbine wake response to first-order turbine control changes. Wind turbine wake response was measured using Texas Tech University's Ka-band Doppler radars and dual-Doppler scanning strategies. Results highlight some of the complexities associated with executing and analyzing wind plant control at full scale using brief experimental control periods. Some difficulties include (1) the ability to accurately implement the desired control changes, (2) identifying reliable data sources and methods to allow these control changes to be accurately quantified, and (3) attributing variations in wake structure to turbine control changes rather than a response to the underlying atmospheric conditions (e.g., boundary layer streak orientation, atmospheric stability). To better understand wake sensitivity to the underlying atmospheric conditions, wake evolution within the early-evening transition was also examined using a single-Doppler data collection approach. Analysis of both wake length and meandering during this period of transitioning atmospheric stability indicates the potential benefit and feasibility of wind plant control should be enhanced when the atmosphere is stable.Published by Copernicus Publications on behalf of the European Academy of Wind Energy e.V.

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Impact of atmospheric stability on wind turbine wake evolution

Cited by 14 publications

References 14 publications

LES Study of Wake Meandering in Different Atmospheric Stabilities and Its Effects on Wind Turbine Aerodynamics

LES Study of Wake Meandering in Different Atmospheric Stabilities and Its Effects on Wind Turbine Aerodynamics

Large eddy simulations of wind turbine wakes in typical complex topographies

Exploring the complexities associated with full-scale wind plant wake mitigation control experiments

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