Influence of the Heights of Low-Level Jets on Power and Aerodynamic Loads of a Horizontal Axis Wind Turbine Rotor

Zhang, Xuyao; Yang, Congxin; Li, Ye

doi:10.3390/atmos10030132

Cited by 9 publications

(5 citation statements)

References 25 publications

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“…The IEC 61400-13 guideline [2] defines the vertical wind shear below hub height as mandatory to be measured, whereas the measurements above are only recommended. In this case, however, abnormal shears above hub height might not be covered, such as low-level jets (LLJs) [41,42,61], although it was found that these phenomena can have a noticeable impact on the turbine loads [62].…”

Section: Test Case 2: Varying Shear Conditionsmentioning

confidence: 98%

Development of a Load Model Validation Framework Applied to Synthetic Turbulent Wind Field Evaluation

Meyer,

Huhn,

Gottschall

2024

Energies

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The validation of aeroelastic load models used for load calculations on wind turbines substantially increases the confidence in the accuracy and correctness of these models. In this contribution, we introduce a framework for the validation of these models, integrating a normalized area metric as an objective, quantifiable validation metric that considers the entire statistical distribution of a model and a benchmark and additionally enables a comparison of model accuracy between sensors of different physical units. The framework is applied to test cases that evaluate varying synthetic turbulent wind fields. Two test cases with a focus on turbulence parameters and abnormal shear conditions based on comprehensive wind measurements at the Testfeld Bremerhaven are used to demonstrate the workflow with four different members using IEC-compliant and measurement-derived wind field parameters, respectively. Along with these measurements, an uncertainty model for synthetic wind fields is introduced to quantify propagated wind measurement uncertainties associated with the measured boundary conditions during a validation campaign. The framework is presented as a straightforward and concise methodology to not only find but also quantify mismatches of load models. Major mismatches are found for wind fields associated with larger uncertainties in the mean wind field due to a reduced spatial resolution of measurements.

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Section: Test Case 2: Varying Shear Conditionsmentioning

confidence: 98%

Development of a Load Model Validation Framework Applied to Synthetic Turbulent Wind Field Evaluation

Meyer,

Huhn,

Gottschall

2024

Energies

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“…For the case of the above-rated wind speed, the relative error increases due to the three-dimensional rotation effect and blade stall, but it is less than 10%. In addition, we also compare the predicted results by the BEM method and those of the CFD method [32] and FAST open-source software [33] The obtained results reveal that the calculation results of the BEM, CFD, and FAST soft ware are also very close, and the relative error does not exceed 5%. Therefore, the program o the BEM method is accurate.…”

Section: Validation Of Bem Theorymentioning

confidence: 99%

Study on the Influence of Low-Level Jet on the Aerodynamic Characteristics of Horizontal Axis Wind Turbine Rotor Based on the Aerodynamics–Controller Interaction Method

Xia

2022

Energies

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Accurate prediction of the aerodynamic characteristics of wind rotors subjected to various wind profiles is of considerable importance in the aerodynamics and structural design of wind turbines. As a very complex atmospheric phenomenon, the impact of a low-level jet (LLJ) on the aerodynamic characteristics of wind rotors is becoming more and more significant with the increase in wind turbine height. Additionally, during calculating the aerodynamic characteristics of the wind rotor, the known wind speed, rotor speed, and blade-pitch angle are generally required. However, when the wind profile is in the LLJ condition, it is difficult to determine the blade-pitch angle and rotor speed. Therefore, in this paper, the blade-element-momentum (BEM) method is exploited by considering the coupling with the generator-torque controller and blade-pitch controller. In order to solve the problem of the unknown rotor speed and blade-pitch angle under the LLJ condition, a C++ code is developed. Then, the influence of the LLJ on the aerodynamic characteristics of the wind rotor is exclusively examined. The research results show that the calculation method can precisely evaluate the rotor speed, blade-pitch angle, and aerodynamic characteristics of the wind rotor. The influence of the LLJ on the aerodynamic loads of the wind rotor is greater than that of the wind shear. When the LLJ is placed inside the rotor swept area, the aerodynamic loads of the blade exhibit two local maximums and local minimums with the variation of the azimuth angle in a rotation period. The closer the LLJ height is to the hub height, the greater the average aerodynamic loads of the wind rotor are, and the smaller the amplitude of aerodynamic loads of the blade is relative to the average value. When the LLJ height is positioned outside the rotor swept area, the change law of the aerodynamic loads of the blade would be similar to that of the wind subjected to a very strong wind shear inflow. This study provides a crucial reference for a more rational assessment of the aerodynamic characteristics of wind turbines under the action of complex wind profiles, as well as revealing the influence of the LLJ on the aerodynamic characteristics of wind turbines.

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“…LLJs are typically associated with stable boundary layers and frequently exhibit much higher veer, positive or negative shear, and lower turbulence intensity than standard neutral or unstable atmospheric conditions. In the context of wind energy, LLJs have been found to produce higher aerodynamic loads [1] as well as higher power production [2], but have not been heavily studied as LLJs on land such as the nocturnal jets in the Southern Great Plains typically exhibit their maximum wind speeds above 300 m altitude [3]. However, recent studies of offshore lease areas in the U.S. Mid-Atlantic region indicate that LLJs occur intermittently at altitudes relevant to an offshore turbine as often as 7% of the time [4].…”

Section: Introductionmentioning

confidence: 99%

Idealized Offshore Low-Level Jets for Turbine Structural Impact Considerations

Jong,

Quon,

Zalkind

2024

Preprint

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Low level jets (LLJs) describe conditions in which the wind speed reaches a local maximum with respect to altitude near the surface, and have been observed intermittently in the US Mid-Atlantic offshore environment. LLJs pose unique operating conditions for future wind turbines operating in the region, presenting negative shear and locally strong veer, but they are not typically considered in existing turbine standards. This work builds upon recent research that explains the formation and evolution of U.S. Mid-Atlantic LLJs through a simple analytical governing equation. We generate several LLJ inflow conditions with varying jet characteristics based on this analytical model and create monotonically-sheared (MS) analogues with constant veer in order to assess the impacts of the LLJ on turbine performance and loading. Using aeroelastic simulations with these inflow conditions on the IEA 15MW reference turbine, we find that the LLJ leads to a greater range of tower top pitching and yawing moments, which could contribute to larger accumulated structural fatigue in components compared to monotonically-sheared inflow. These preliminary results demonstrate a path toward a unified set of test cases for low-level wind maxima that can inform International Electrotechnical Commission standards related to offshore wind turbine design.

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Influence of the Heights of Low-Level Jets on Power and Aerodynamic Loads of a Horizontal Axis Wind Turbine Rotor

Cited by 9 publications

References 25 publications

Development of a Load Model Validation Framework Applied to Synthetic Turbulent Wind Field Evaluation

Development of a Load Model Validation Framework Applied to Synthetic Turbulent Wind Field Evaluation

Study on the Influence of Low-Level Jet on the Aerodynamic Characteristics of Horizontal Axis Wind Turbine Rotor Based on the Aerodynamics–Controller Interaction Method

Idealized Offshore Low-Level Jets for Turbine Structural Impact Considerations

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