Parametric dependencies of the yawed wind‐turbine wake development

Kleusberg, Elektra; Schlatter, Philipp; Henningson, Dan S.

doi:10.1002/we.2395

Cited by 14 publications

(12 citation statements)

References 24 publications

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“…First, the interaction between wake rotation and the ground has been shown to substantially influence the vertical displacement of the wake centre during yaw (Bastankhah & Porté-Agel 2016). Furthermore, Kleusberg, Schlatter & Henningson (2020) showed that the angle of attack of the blades varies between the top and bottom of the rotor when the turbine is yawed, introducing an additional source of vertical asymmetry. Finally, differences in spanwise vorticity between the top and bottom of the rotor may contribute to changes in the vertical velocity field of the wake.…”

Section: Resultsmentioning

confidence: 99%

Mechanisms of dynamic near-wake modulation of a utility-scale wind turbine

2021

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The current study uses large eddy simulations to investigate the transient response of a utility-scale wind turbine wake to dynamic changes in atmospheric and operational conditions, as observed in previous field-scale measurements. Most wind turbine wake investigations assume quasi-steady conditions, but real wind turbines operate in a highly stochastic atmosphere, and their operation (e.g. blade pitch, yaw angle) changes constantly in response. Furthermore, dynamic control strategies have been recently proposed to optimize wind farm power generation and longevity. Therefore, improved understanding of dynamic wake behaviours is essential. First, changes in blade pitch are investigated and the wake expansion response is found to display hysteresis as a result of flow inertia. The time scales of the wake response to different pitch rates are quantified. Next, changes in wind direction with different time scales are explored. Under short time scales, the wake deflection is in the opposite direction of that observed under quasi-steady conditions. Finally, yaw changes are implemented at different rates, and the maximum inverse wake deflection and time scale are quantified, showing a clear dependence on yaw rate. To gain further physical understanding of the mechanism behind the inverse wake deflection, the streamwise vorticity in different parts of the wake is quantified. The results of this study provide guidance for the design of advanced wake flow control algorithms. The lag in wake response observed for both blade pitch and yaw changes shows that proposed dynamic control strategies must implement turbine operational changes with a time scale of the order of the rotor time scale or slower.

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Section: Resultsmentioning

confidence: 99%

Mechanisms of dynamic near-wake modulation of a utility-scale wind turbine

2021

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“…2017; Mühle et al. 2018; Kleusberg 2019; Kleusberg, Schlatter & Henningson 2020). Since the focus of those studies was on the wake and on total forces, the errors caused by the approximation of the tip correction were not considered to greatly affect the results.…”

Section: Methodsmentioning

confidence: 99%

Non-iterative vortex-based smearing correction for the actuator line method

2023

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The actuator line method (ALM) is used extensively in wind turbine and rotor simulations. However, its original uncorrected formulation overestimates the forces near the tip of the blades and does not reproduce well forces on translating wings. The recently proposed vortex-based smearing correction for the ALM is a correction based on physical and mathematical properties of the simulation that allows for a more accurate and general ALM. So far, to correct the forces on the blades, the smearing correction depended on an iterative process at every time step, which is usually slower, less stable and less deterministic than direct methods. In this work, a non-iterative process is proposed and validated. First, we propose a formulation of the nonlinear lifting line that is equivalent to the ALM with smearing correction, showing that the results are practically identical for a translating wing. Then, by linearizing the lifting line method, the iterative process of the correction is substituted by the direct solution of a small linear system. No significant difference is observed in the results of the iterative and non-iterative corrections, in both wing and rotor simulations. Additional contributions of the present work include the use of a more accurate approximation for the velocity induced by a smeared vortex segment and the implementation of a free-vortex wake model to define the vortex sheet, which contribute to the accuracy and generality of the method. The results presented here may motivate the adoption of the ALM by other communities, for example, in fixed-wing applications.

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“…The actuator line was previously implemented in Nek5000 (Kleusberg et al 2016, 2017, Kleusberg 2019) with Prandtl's tip correction. The code was extensively validated, showing good agreement between numerical and experimental results (Kleusberg et al 2017, Mühle et al 2018, Kleusberg 2019, Kleusberg et al 2020. Since the focus of those studies were on the wake and on total forces, the errors caused by the approximation of the tip correction were not considered to greatly affect the results.…”

Section: Numerical Solver Of Navier-stokes Equations With the Actuato...mentioning

confidence: 99%

Non-iterative vortex-based smearing correction for the actuator line method

Kleine¹,

Hanifi²,

Henningson³

2022

Preprint

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The actuator line method (ALM) is extensively used in wind turbine and rotor simulations. However, its original uncorrected formulation overestimates the forces near the tip of the blades and does not reproduce well forces on translating wings. The recently proposed smearing correction for the ALM is a correction based on physical and mathematical properties of the simulation that allows for a more accurate and general ALM. So far, to correct the forces on the blades, the smearing correction depended on an iterative process at every time step, which is usually slower, less stable and less deterministic than direct methods. In this work, a non-iterative process is proposed and validated. First, we propose a formulation of the non-linear lifting line that is equivalent to the ALM with smearing correction, showing that their results are practically identical for a translating wing. Then, by linearizing the lifting line method, the iterative process of the correction is substituted by the direct solution of a small linear system. No significant difference is observed in the results of the iterative and non-iterative corrections, both in wing and rotor simulations. Additional contributions of the present work include the use of a more accurate approximation for the velocity induced by a smeared vortex segment and the implementation of a free-vortex wake model to define the vortex sheet, that contribute to the accuracy and generality of the method. The results present here may motivate the adoption of the ALM by other communities, for example, in fixed-wing applications.

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Parametric dependencies of the yawed wind‐turbine wake development

Cited by 14 publications

References 24 publications

Mechanisms of dynamic near-wake modulation of a utility-scale wind turbine

Mechanisms of dynamic near-wake modulation of a utility-scale wind turbine

Non-iterative vortex-based smearing correction for the actuator line method

Non-iterative vortex-based smearing correction for the actuator line method

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