A simple model of the wind turbine induction zone derived from numerical simulations

Troldborg, Niels; Forsting, Alexander Meyer

doi:10.1002/we.2137

Cited by 62 publications

(70 citation statements)

References 18 publications

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“…For wind speeds below rated the induction factor reaches levels above 0.4, which is higher than the expectation of approximately 0.3. The reason for this is that the quasi-steady model assumes a uniform load distribution and therefore tends to underestimate the induced velocity of real rotors, which have a nonuniform loading, as shown by Troldborg and Meyer Forsting (2017). For a given C T , this bias causes an overestimation of the induction factor when the model is fitted to measurements of the upstream velocity.…”

Section: Resultsmentioning

confidence: 99%

“…For a given C T , this bias causes an overestimation of the induction factor when the model is fitted to measurements of the upstream velocity. The bias is particularly dominant for the Siemens 2.3 MW because it has a high local loading below rated wind speed; see Troldborg and Meyer Forsting (2017). Figure 3a shows values of the measured u(x)/U ∞ averaged in intervals of U ∞ with fits of Eq.…”

Section: Resultsmentioning

confidence: 99%

“…The C T curve used in the present AD simulations is obtained from steady-state simulations of the Siemens turbine presented by Troldborg and Meyer Forsting (2017) with a rated power of 2.3 MW at 11.5 m s −1 . From their simulations, we also extract the relation between U ∞ and U disk and thereby the C * T curve.…”

Section: Wind Turbine Modelmentioning

confidence: 99%

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How does turbulence change approaching a rotor?

et al. 2018

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Abstract. For load calculations on wind turbines it is usually assumed that the turbulence approaching the rotor does not change its statistics as it goes through the induction zone. We investigate this assumption using a nacelle-mounted forward-looking pulsed lidar that measures low-frequency wind fluctuations simultaneously at distances between 0.5 and 3 rotor diameters upstream. The measurements show that below rated wind speed the low-frequency wind variance is reduced by up to 10 % at 0.5 rotor diameters upstream and above rated enhanced by up to 20 %. A quasi-steady model that takes into account the change in thrust coefficient with wind speed explains these variations partly. Large eddy simulations of turbulence approaching an actuator disk model of a rotor support the finding that the slope of the thrust curve influences the low-frequency fluctuations.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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How does turbulence change approaching a rotor?

et al. 2018

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“…This influence is measurable more than one diameter upstream (Meyer Forsting et al, 2017) and continues until the wake is recovered far downstream. This means that a model or calibration function is required to estimate the free-flow wind speed from a nacelle-or spinner-mounted anemometer.…”

Section: Introductionmentioning

confidence: 96%

Free-flow wind speed from a blade-mounted flow sensor

et al. 2018

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Abstract. This paper presents a method for obtaining the free-inflow velocities from a 3-D flow sensor mounted on the blade of a wind turbine.From its position on the rotating blade, e.g. one-third from the tip, a blade-mounted flow sensor (BMFS) is able to provide valuable information about the turbulent sheared inflow in different regions of the rotor. At the rotor, however, the inflow is affected by the wind turbine, and in most cases the wind of interest is the inflow that the wind turbine is exposed to, i.e. the free-inflow velocities.The current method applies a combination of aerodynamic models and procedures to estimate the induced velocities, i.e. the disturbance of the flow field caused by the wind turbine. These velocities are subtracted from the flow velocities measured by the BMFS to obtain the free-inflow velocities. Aeroelastic codes, like HAWC2, typically use a similar approach to calculate the induction, but they use it for the reversed process, i.e. they add the induction to the free inflow to get the flow velocities at the blades, which are required to calculate the resulting aerodynamic forces.The aerodynamic models included in the current method comprise models based on blade element momentum (BEM) for axial and tangential induction, a radial induction model and tip loss correction, and models for skew and dynamic inflow.It is shown that the method is able to calculate the free-inflow velocities with high accuracy when applied to aeroelastic HAWC2 simulations with a stiff structural model while some deviations are seen in simulations with a flexible structure.Furthermore, the method is tested on simulations performed by a flexible structural model coupled with a large-eddy simulation (LES) flow solver. The results of this higher-fidelity verification confirm the HAWC2-based conclusion.

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“…Recent studies of these changes to the incoming wind in the induction zone comprise steady state consideration by Troldborg and Forsting [1] and the change in the low frequency part of the spectra by Mann et al [2].…”

Section: Introductionmentioning

confidence: 99%

Instantaneous Response and Mutual Interaction between Wind Turbine and Flow

Andersen¹,

Sørensen²

2018

J. Phys.: Conf. Ser.

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Abstract. The mutual fluid-structure interaction between wind turbine(s) and the highly turbulent flow deep inside a large wind farm is investigated in order to elucidate on how to implement and perform dynamic wind farm control. The study employs a fully coupled LES and aeroelastic framework, which provide time resolved flow and turbine response governed by a controller. The results show a large correlation between incoming flow and turbine response, which extends several radii upstream and could be utilized for turbine control by e.g. installing a lidar on top of the wind turbine. Similarly, the results are valuable for utilizing nacelle mounted lidars for power curve assessments in large wind farms. However, the correlations between turbine and wake flow as well as the dynamic wake position are low, which is potentially discouraging for attempts to do instantaneous yaw steering.

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A simple model of the wind turbine induction zone derived from numerical simulations

Cited by 62 publications

References 18 publications

How does turbulence change approaching a rotor?

How does turbulence change approaching a rotor?

Free-flow wind speed from a blade-mounted flow sensor

Instantaneous Response and Mutual Interaction between Wind Turbine and Flow

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