Numerical investigation of wind turbine wake development in directionally sheared inflow

Bromm, Marc; Vollmer, Lukas; Kühn, Martin

doi:10.1002/we.2010

Cited by 40 publications

(28 citation statements)

References 28 publications

(24 reference statements)

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“…As can be visually acknowledged, due to the lateral component of the incoming wind, the wake is skewed as it is advected downstream. This is a well-known phenomenon and has been shown in several field-scale and numerical investigations of wake flow in the stable regimes [1][2][3][4][5][6][7][8]10]. …”

Section: Les Resultsmentioning

confidence: 99%

“…Much work, including numerical simulations and field-scale measurements [1][2][3][4][5][6][7][8][9], has been done recently to unravel the impact of lateral wind shear (also known as vertical wind veer) on the aerodynamics of wind turbine wakes. All these studies highlighted that, for the large utility-scale wind turbines, the impact of the lateral wind shear cannot be ignored.…”

Section: Introductionmentioning

confidence: 99%

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An Analytical Model for the Effect of Vertical Wind Veer on Wind Turbine Wakes

2018

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Abstract:In this study, an analytical wake model for predicting the mean velocity field downstream of a wind turbine under veering incoming wind is systematically derived and validated. The new model, which is an extended version of the one introduced by Bastankhah and Porté-Agel, is based upon the application of mass conservation and momentum theorem and considering a skewed Gaussian distribution for the wake velocity deficit. Particularly, using a skewed (instead of axisymmetric) Gaussian shape allows accounting for the lateral shear in the incoming wind induced by the Coriolis force. This analytical wake model requires only the wake expansion rate as an input parameter to predict the mean wake flow downstream. The performance of the proposed model is assessed using the large-eddy simulation (LES) data of a full-scale wind turbine wake under the stably stratified condition. The results show that the proposed model is capable of predicting the skewed structure of the wake downwind of the turbine, and its prediction for the wake velocity deficit is in good agreement with the high-fidelity simulation data.

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Section: Les Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Analytical Model for the Effect of Vertical Wind Veer on Wind Turbine Wakes

2018

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“…Measurements at lower heights were not included in the analysis because of the technical restrictions of the lidar. Wind veer is attributed to the force balance between friction, pressure gradient, and Coriolis force, and it was shown in simulations and field experiments that it leads to the development of a nonrotationally symmetric wake shape.

δ = β_{L} false(h_{2} false) - β_{L} false(h_{1} false)

A positive value of δ indicates clockwise rotation with increasing height, which we expect in the northern hemisphere because of the effect of the Coriolis force.…”

Section: Methodsmentioning

confidence: 99%

Field investigation on the influence of yaw misalignment on the propagation of wind turbine wakes

et al. 2018

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A comprehensive understanding of the wake development of wind turbines is essential for improving the power yield of wind farms and for reducing the structural loading of the turbines.Reducing the overall negative impact of wake flows on individual turbines in a farm is one goal of wind farm control. We aim to demonstrate the applicability of yaw control for deflecting wind turbine wakes in a full-scale field experiment. For this purpose, we conducted a measurement campaign at a multimegawatt onshore wind turbine including inflow and wake flow measurements using ground-and nacelle-based long-range light detection and ranging devices. Yaw misalignments of the turbine with respect to the inflow direction of up to 20 • were investigated. We were able to show that under neutral atmospheric conditions, these turbine misalignments cause lateral deflections of its wake. Larger yaw misalignments resulted in greater wake deflection.Because of the inherent struggle in capturing complex and highly dynamic ambient conditions in the field using a limited number of sensors, we particularly focused on providing a comprehensive and comprehensible description of the measurement setup, including the identification of potential uncertainties. KEYWORDSatmospheric boundary layer, atmospheric inflow, lidar, wake deflection, wind farm control INTRODUCTIONWind turbines in a wind farm are typically subjected to mutual aerodynamic interactions due to their wakes. Depending on the farm layout and inflow direction, this can lead to unfavourable structural loading and a substantial reduction in the power yield over extended periods of time . 1-3 Reducing the overall negative impact of wake flows on individual turbines in a farm is one goal of wind farm control. However, a successful implementation of control mechanisms requires a broad understanding of the flow development for various ambient conditions and the interaction between turbines and the flow.One specific approach that has proven its potential in simulations and wind tunnel experiments is wake deflection through turbine operation under yaw misalignment. In this case, an offset between the inflow direction and the orientation of a turbine is deliberately introduced to alter its wake trajectory. Hereinafter, we refer to this method as yaw control for the sake of simplicity. It aims to generate more favourable inflow conditions for downstream turbines by reducing the wake effects. This can, for example, be used to maximize the power output of a wind farm, to mitigate power fluctuation or to reduce turbine loads. With respect to power maximization, it should be considered that misaligned wind turbines generate less power. Therefore, it must be ensured that the power increase generated by the downstream turbines is sufficient for improving the overall power yield of the wind farm.The concept of wake deflection has already been successfully applied in wind tunnel experiments by Clayton and Filby in 1982. 4 Further investigations of the power yield and characteristics of the downstream d...

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“…Ivanell et al [35] studied stability properties of wind turbine wakes using a CFD model based on the LES ALM on the tip vortices of the Tjaereborg wind turbine. Bromm et al [36] investigated the impact of directionally sheared inflow in the wake development, and analysis of the impact of wakes on energy production and loading on a downstream turbine. A LES was performed using the ALM representation.…”

Section: Nrel 5 Mwmentioning

confidence: 99%

Development of a Computational System to Improve Wind Farm Layout, Part II: Wind Turbine Wakes Interaction

Rodrigues

Lengsfeld

2019

Energies

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The second part of this work describes a wind turbine Computational Fluid Dynamics (CFD) simulation capable of modeling wake effects. The work is intended to establish a computational framework from which to investigate wind farm layout. Following the first part of this work that described the near wake flow field, the physical domain of the validated model in the near wake was adapted and extended to include the far wake. Additionally, the numerical approach implemented allowed to efficiently model the effects of the wake interaction between rows in a wind farm with reduced computational costs. The influence of some wind farm design parameters on the wake development was assessed: Tip Speed Ratio (TSR), free-stream velocity, and pitch angle. The results showed that the velocity and turbulence intensity profiles in the far wake are dependent on the TSR. The wake profile did not present significant sensitivity to the pitch angle for values kept close to the designed condition. The capability of the proposed CFD model showed to be consistent when compared with field data and kinematical models results, presenting similar ranges of wake deficit. In conclusion, the computational models proposed in this work can be used to improve wind farm layout considering wake effects.

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Numerical investigation of wind turbine wake development in directionally sheared inflow

Cited by 40 publications

References 28 publications

An Analytical Model for the Effect of Vertical Wind Veer on Wind Turbine Wakes

An Analytical Model for the Effect of Vertical Wind Veer on Wind Turbine Wakes

Field investigation on the influence of yaw misalignment on the propagation of wind turbine wakes

Development of a Computational System to Improve Wind Farm Layout, Part II: Wind Turbine Wakes Interaction

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