Characterization of a wind turbine wake evolving over an intertidal zone performed with dual-lidar observations

Abstract. As modern wind power industry quickly develops, it is of high priority to optimize layouts and operations of wind turbines to reduce the influences of wakes induced by upstream wind turbines. The wake behaves complicatedly with land ocean-atmosphere interactions. This complex wake could be observed by two or more synchronously operated Doppler lidars. Accordingly, we characterized a wind turbine wake evolving over an intertidal zone performed with dual-lidar observations. Dynamic process of wakes merging that occurred from approximately 1 D (rotor diameter) downstream was captured and analysed. The phenomenon that wake length increased with rising tide was analysed in details. It suggested that the increase of wake length varied with underlying surface roughness transition from mud to sea water as well as the rising sea level. Finally, wake meandering cases were analyzed in detail. Our research shows that the dual-lidar observation technology is a promising remote sensing tool for characterization of complicated wind turbine wakes.

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Investigation of the dissipation in the wake of a wind turbine array

10.5194/wes-2021-13 ◽

2021 ◽

Author(s):

Ingrid Neunaber ◽

Joachim Peinke ◽

Martin Obligado

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Bluff Body ◽

Wind Farms ◽

Energy Transition ◽

Mean Velocity ◽

Maintenance Time ◽

Bluff Body Wake ◽

Turbine Wake ◽

Wind Turbine Wake

Abstract. Within the energy transition, more and more wind turbines are clustered in big wind farms, often offshore. Therefore, an optimal positioning of the wind turbines is crucial to optimize both the annual power production and the maintenance time. Good knowledge of the wind turbine wake and the turbulence within is thus important. However, although wind turbine wakes have been subject to various studies, they are still not fully understood. One possibility to improve the comprehension is to look into the modeling of bluff body wakes. These wakes have been the subject of intensive study for decades, and by means of the scaling behavior of the centerline mean velocity deficit, the nature of the turbulence inside a wake can be classified. In this paper, we introduce the models for equilibrium and non-equilibrium turbulence from classical wake theory as introduced by A. Townsend and W. George, and we test whether the requirements are fulfilled in the wake of a wind turbine. Finally, we apply the theory to characterize the wind turbine wake, and we compare the results to the Jensen and the Bastankhah-Porté-Agel model. We find that the insight into the classical bluff body wake can be used to further improve the wind turbine wake models. Particularly, the classical bluff body wake models perform better than the wind turbine wake models due to the presence of a virtual origin in the scalings, and we demonstrate the possibility of improving the wind turbine wake models by implementing this parameter. We also see how the dissipation changes across the wake which is important to model wakes within wind farms correctly.

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Volumetric Lidar Scanning of Wind Turbine Wakes under Convective and Neutral Atmospheric Stability Regimes

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-13-00252.1 ◽

2014 ◽

Vol 31 (10) ◽

pp. 2035-2048 ◽

Cited By ~ 63

Author(s):

Giacomo Valerio Iungo ◽

Fernando Porté-Agel

Keyword(s):

Thermal Stability ◽

Wind Turbine ◽

Wind Power ◽

Wind Velocity ◽

Turbulence Intensity ◽

Atmospheric Stability ◽

Power Harvesting ◽

Turbine Wake ◽

Wind Turbine Wake

Abstract Optimization of a wind farm’s layout is a strategic task to reduce wake effects on downstream turbines, thus maximizing wind power harvesting. However, downstream evolution and recovery of each wind turbine wake are strongly affected by the characteristics of the incoming atmospheric boundary layer (ABL) flow, such as the vertical profiles of the mean wind velocity and the turbulence intensity, which are in turn affected by the ABL thermal stability. Therefore, the characterization of the variability of wind turbine wakes under different ABL stability regimes becomes fundamental to better predict wind power harvesting and to improve wind farm efficiency. To this aim, wind velocity measurements of the wake produced by a 2-MW Enercon E-70 wind turbine were performed with three scanning Doppler wind lidars. One lidar was devoted to the characterization of the incoming wind—in particular, wind velocity, shear, and turbulence intensity at the height of the rotor disc. The other two lidars performed volumetric scans of the wind turbine wake under different atmospheric conditions. Through the evaluation of the minimum wake velocity deficit as a function of the downstream distance, it is shown that the ABL stability regime has a significant effect on the wake evolution; in particular, the wake recovers faster under convective conditions. This result suggests that atmospheric inflow conditions, and particularly thermal stability, should be considered for improved wake models and predictions of wind power harvesting.

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Characterization of the SUMO Turbulence Measurement System for Wind Turbine Wake Assessment

Energy Procedia ◽

10.1016/j.egypro.2014.07.226 ◽

2014 ◽

Vol 53 ◽

pp. 173-183 ◽

Cited By ~ 5

Author(s):

Line Båserud ◽

Martin Flügge ◽

Anak Bhandari ◽

Joachim Reuder

Keyword(s):

Wind Turbine ◽

Measurement System ◽

Turbulence Measurement ◽

Turbine Wake ◽

Wind Turbine Wake

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Simple Wake Models for Tidal Turbines in Farm Arrangement

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 3 ◽

10.1115/omae2010-20966 ◽

2010 ◽

Cited By ~ 1

Author(s):

Moritz Palm ◽

Rene Huijsmans ◽

Mathieu Pourquie ◽

Anne Sijtstra

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Reference Data ◽

Energy Output ◽

Cfd Model ◽

Tidal Turbines ◽

Tidal Turbine ◽

Wake Model ◽

Turbine Wake ◽

Wind Turbine Wake

From wind turbines it is known that the wake, induced by a turbine, has a negative impact on the energy production of downstream devices. Basically, the wake is a zone with reduced velocity behind a turbine. Further downstream, the velocity recovers gradually by turbulent mixing with the ambient flow. In order to optimize the design of a tidal farm, the aim of this paper is to find simple relations that can be used to predict the energy output of a given farm configuration. The energy output of a turbine depends on its inflow velocity. Therefore, the strategy is to find a model that is able to predict the velocity field in the tidal farm. Such ‘wake models’ exist already for wind turbines and thruster-thruster interaction. In this research, the applicability of these wake models to tidal turbines is investigated by comparing their results to reference data of tidal turbines. Only limited measurement data for tidal turbines are available; therefore a CFD model of a tidal turbine is used to generate the reference data. The velocity in the wake is simulated for different conditions with the CFD model. The CFD model is validated with the available data in the literature. The velocity in the wake for a single turbine is predicted accurately for different initial conditions. Modeling of the turbulence showed some discrepancies in the far wake, consequently the wake of turbines in farm configurations is predicted less accurate. Three wake models, selected from the literature, are compared to the CFD simulations of the wake behind a single turbine. The wind turbine wake model of Jensen performed best; the velocity in the wake is calculated accurate for different situations. Mutual interaction of wakes will occur inside tidal farms. Several methods from wind turbines theory are used to estimate the velocity in interaction situations. Three basic situations of wake interaction are distinguished: tandem operation, wake interference and overlapping inflow. The interaction methods are tested with CFD reference data for each situation separately. Most methods compared reasonably well; the most suitable interaction methods are selected. A small tidal farm case study is performed to test the combination of wake model and interaction methods. The flow in the cluster of 5 turbines is predicted satisfactorily by the wake model for different inflow velocities. All results indicate that the principle of applying wind turbine wake models to tidal turbine has good potential. However the number of test cases conducted in the thesis is limited and the incorrect turbulence modeling of the CFD model caused some uncertainties for multiple turbine situation.

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A Modified Reynolds-Averaged Navier–Stokes-Based Wind Turbine Wake Model Considering Correction Modules

Energies ◽

10.3390/en13174430 ◽

2020 ◽

Vol 13 (17) ◽

pp. 4430

Author(s):

Yuan Li ◽

Zengjin Xu ◽

Zuoxia Xing ◽

Bowen Zhou ◽

Haoqian Cui ◽

...

Keyword(s):

Power Generation ◽

Power Systems ◽

Wind Turbine ◽

Turbulence Model ◽

Wind Turbines ◽

Navier Stokes ◽

Aerodynamic Model ◽

Wake Model ◽

Turbine Wake ◽

Wind Turbine Wake

Increasing wind power generation has been introduced into power systems to meet the renewable energy targets in power generation. The output efficiency and output power stability are of great importance for wind turbines to be integrated into power systems. The wake effect influences the power generation efficiency and stability of wind turbines. However, few studies consider comprehensive corrections in an aerodynamic model and a turbulence model, which challenges the calculation accuracy of the velocity field and turbulence field in the wind turbine wake model, thus affecting wind power integration into power systems. To tackle this challenge, this paper proposes a modified Reynolds-averaged Navier–Stokes (MRANS)-based wind turbine wake model to simulate the wake effects. Our main aim is to add correction modules in a 3D aerodynamic model and a shear-stress transport (SST) k-ω turbulence model, which are converted into a volume source term and a Reynolds stress term for the MRANS-based wake model, respectively. A correction module including blade tip loss, hub loss, and attack angle deviation is considered in the 3D aerodynamic model, which is established by blade element momentum aerodynamic theory and an improved Cauchy fuzzy distribution. Meanwhile, another correction module, including a hold source term, regulating parameters and reducing the dissipation term, is added into the SST k-ω turbulence model. Furthermore, a structured hexahedron mesh with variable size is developed to significantly improve computational efficiency and make results smoother. Simulation results of the velocity field and turbulent field with the proposed approach are consistent with the data of real wind turbines, which verifies the effectiveness of the proposed approach. The variation law of the expansion effect and the double-hump effect are also given.

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