Comparative study on the wake deflection behind yawed wind turbine models

Schottler, Jannik; Mühle, Franz; Bartl, Jan; Peinke, Joachim; Adaramola, Muyiwa S.; Sætran, Lars Roar; Hölling, Michael

doi:10.1088/1742-6596/854/1/012032

Cited by 28 publications

(32 citation statements)

References 14 publications

(18 reference statements)

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“…This can also be seen in Figure 11, where speed-up effects are visible in the corners. In Schottler et al (2017b), where the same setup was used 1 , the skew angle for the NTNU rotor decreased from x/D = 3 to x/D = 6, which is a further indication for wall effects due to blockage, especially during yaw misalignment. Furthermore, both values show smaller angles as for the ForWind turbine.…”

Section: Wakes During Yaw-misalignmentmentioning

confidence: 96%

“…The turbines will be denoted NTNU and ForWind, respectively. Table 1 summarizes the main features and differences of both turbines, further details are described by Schottler et al (2017b). Figure 1 shows technical drawings.…”

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confidence: 99%

“…In order to quantify the lateral wake position, we compute the power of a potential downstream turbine as described by Schottler et al (2017b). A similar approach was shown by Vollmer et al (2016).…”

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confidence: 99%

“…The airfoil of 5 the NTNU turbine (NREL S826) has higher lift coefficients for the relevant angles of attack and Reynolds numbers compared to the ForWind rotor (SD7003 airfoil). A comparison of both airfoils is given in Schottler et al (2017b). As a result, larger pressure differences between suction and pressure side of the blades are expected, resulting in more pronounced tip vortices shed from the NTNU rotor.…”

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confidence: 99%

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Wind tunnel experiments on wind turbine wakes in yaw: Redefining the wake width

Schottler¹,

Bartl²,

Mühle³

et al. 2018

Preprint

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Abstract. This paper presents an investigation of wakes behind model wind turbines, including cases of yaw misalignment. Two different turbines were used and their wakes are compared, isolating effects of boundary conditions and turbine specifications. The results show that areas of strongly heavy-tailed distributed velocity increments are surrounding the velocity deficit in all cases examined. Thus, a wake is significantly wider when two-point statistics are included as opposed to a description limited to one-point quantities. As non-Gaussian distributions of velocity increments affect loads of downstream rotors, our findings impact the application of active wake steering through yaw misalignment as well as wind farm layout optimizations and should 10 therefore be considered in future wake studies, wind farm layout and farm control approaches. Further, the velocity deficits behind both turbines are deformed to a kidney-like curled shape during yaw misalignment, for which parameterization methods are introduced. Moreover, the lateral wake deflection during yaw misalignment is investigated.

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Section: Wakes During Yaw-misalignmentmentioning

confidence: 96%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Wind tunnel experiments on wind turbine wakes in yaw: Redefining the wake width

Schottler¹,

Bartl²,

Mühle³

et al. 2018

Preprint

Self Cite

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show abstract

“…Further, based on Porté-Agel (2014, 2016); Niayifar and Porté-Agel (2015), the change in thrust also impacts recovery rate. Wind tunnel tests in Schottler et al (2017) and Bartl and Saetran (2017) show good agreement overall with these latest models.…”

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confidence: 56%

From wake steering to flow control

Fleming¹,

Annoni²,

Churchfield³

et al. 2017

Preprint

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Abstract. In this paper, we investigate the role of flow structures generated in wind farm control through yaw misalignment. A pair of counter-rotating vortices are shown to be important in deforming the shape of the wake and in explaining the asymmetry of wake steering in oppositely signed yaw angles. We motivate the development of new physics for control-oriented engineering models of wind farm control, which include the effects of these large-scale flow structures. Such a new model would improve the predictability of control-oriented models. Results presented in this paper indicate that wind farm control strategies, based 5 on new control-oriented models with new physics, that target total flow control over wake redirection may be different, and perhaps more effective, than current approaches. We propose that wind farm control and wake steering should be thought of as the generation of large-scale flow structures, which will aid in the improved performance of wind farms.

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Improving the efficiency of wind farms via wake manipulation

2018

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Wind turbine farms suffer from wake losses, where the downstream turbines generate less power, and/or the leading turbines are throttled to reduce the downstream power losses. In this paper, we focus on possible external modifications that can enhance the wind turbines' performance when they are operating in a farm environment. In particular, this study is interested in enhancing the performance of the downstream turbines in wind farms. The idea is to move each turbine's wake down and away from subsequent turbines. This goal is achieved by using stationary external airfoils that are placed in proximity to the rotating blades. A number of different designs are tested and the design concepts are tested using Reynolds‐Averaged Navier‐Stokes simulations of an aligned array of 2 wind turbines. The turbines are modeled as actuator disks with axial induction and are placed in a velocity field that is modeled as a turbulent atmospheric boundary layer. It is found that fixed external airfoils can enable partial or full power recovery at turbine separations of as small as 3 rotor diameters downstream. We will also demonstrate that some devices can also improve the performance of the upstream turbine. The physical reasons for these power recovery phenomena are discussed.

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Comparative study on the wake deflection behind yawed wind turbine models

Cited by 28 publications

References 14 publications

Wind tunnel experiments on wind turbine wakes in yaw: Redefining the wake width

Wind tunnel experiments on wind turbine wakes in yaw: Redefining the wake width

From wake steering to flow control

Improving the efficiency of wind farms via wake manipulation

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