Wind Turbine Response in Waked Inflow: A Modelling Benchmark Against Full-Scale Measurements

Asmuth, Henrik; Diaz, Gonzalo Pablo Navarro; Madsen, Helge Aagaard; Branlard, Emmanuel; Forsting, Alexander Meyer; Nilsson, Karl; Jonkman, Jason; Ivanell, Stefan

doi:10.2139/ssrn.3940154

Cited by 3 publications

(3 citation statements)

References 69 publications

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“…From the results obtained in this mesh sensitivity study, the resolution D/32 has been chosen for the simulations in this work. This choice aligns with recommendations from other authors for ALM simulation in uniform and turbulent ABL inflow (Asmuth et al, 2020(Asmuth et al, , 2022.…”

Section: Single Wind Turbinesupporting

confidence: 75%

“…The study of the variation of WT power output for different inflow conditions is also important for determining the necessary fill-in power needed to follow a signal from the grid operator (Bossuyt et al, 2016). The well-known excessive computational cost that constrains the usability of LES based on Navier Stokes equations implementations on central processing units (CPUs) has been drastically reduced due to the new implementations in graphics processing units (GPUs), for example using the Lattice Boltzmann method (Asmuth et al, 2022), making LES studies accessible for large wind farms and in long time periods. One of the challenges when simulating transient WT wake problems is the need for access to detailed wind turbine data, such as the operating setting and the geometric and aerodynamic characteristics of the blade.…”

Section: Introductionmentioning

confidence: 99%

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Actuator line model using simplified force calculation methods

Diaz

Otero

Asmuth

et al. 2022

Preprint

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Abstract. To simulate transient wind turbine wake interaction problems using limited wind turbine data, two new variants of the actuator line technique are proposed in which the rotor blade forces are computed locally using generic load data. The proposed models, which are extensions of the actuator disc force models proposed by Navarro Diaz et al. (2019a) and Sørensen et al. (2020), only demand thrust and power coefficients and the tip speed ratio as input parameters. In the paper it is shown the analogy between the Actuator Disc Method (ADM) and the Actuator Line Method (ALM) and from this derive a simple methodology to implement local forces in the ALM without the need for knowledge of blade geometry and local airfoil data. Two simplified variants of ALMs are proposed, an analytical one based on Sørensen et al. (2020) and a numerical one based on Navarro Diaz et al. (2019a). The proposed models are compared to the ADM, using analogous data, as well as to the classical ALM based on blade element theory, which provides more detailed force distributions by using airfoil data. To evaluate the local force calculation, the analysis of a partial wake interaction case between two wind turbines is carried out for an uniform laminar inflow and for a turbulent neutral atmospheric boundary layer inflow. The computations are performed using the Large Eddy Simulation facility in OpenFOAM, including SOWFA libraries and the reference NREL 5MW wind turbine as test case. In the single turbine case, computed normal and tangential force distributions along the blade showed a very good agreement between the employed models. The two new ALMs exhibited the same distribution as the ALM based on geometry and airfoil data, with minor differences due to the particular tip correction needed in the ALM. For the challenging partially impacted wake case, the analytical and numerical approaches manage both to correctly capture the force distribution at the different regions of the rotor area, with, however, a consistent overestimation of the normal force outside the wake and an underestimation inside the wake. The analytical approach shows a slightly better performance in wake impact cases compared to the numerical one. As expected, the ALMs gave a much more detailed prediction of the higher frequency power output fluctuations than the ADM. These promising findings open the possibility to simulate commercial wind farms in transient inflows using ALM, without having to get access to actual wind turbine and airfoil data, which in most cases are restricted due to confidentiality.

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Section: Single Wind Turbinesupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Actuator line model using simplified force calculation methods

Diaz

Otero

Asmuth

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…However, higher order accuracy pseudo spectral solvers exhibited lower diffusivity and thus later near-to far-wake transition. Six model frameworks are compared to results from the DanAero experiment in [6]. The benchmark includes models of different fidelity and found that integral quantities such as power were well captured by all models, whereas LES predicted second-order statistics of the flow field more accurately.…”

Section: Introductionmentioning

confidence: 99%

Validation of a Lattice Boltzmann Solver Against Wind Turbine Response and Wake Measurements

Korb

Asmuth

Ivanell

2023

J. Phys.: Conf. Ser.

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Two of the major limitations facing the adoption of large-eddy simulation (LES) to the industry today are a lack of validation against full-scale measurements and the high computational cost. The lattice Boltzmann method is an approach to conduct LES that is suitable for parallelization on graphics processing units, leading to reduction in energy-to-solution by multiple orders of magnitude compared to Navier-Stokes solvers. We validate the lattice Boltzmann solver VirtualFluids against the measurements published in the SWiFT benchmark and the results obtained with LES by the participants in the benchmark. We compare inflow, turbine response and wake quantities and show that our method yields similar results. While the other LES methods vary in the required energy by one order of magnitude, our methodology is always about one to two orders of magnitude more efficient. The benchmark allows for a comparison to a large number of models, however, the scale of the turbine is not representative of modern turbines and therefore important challenges of modern turbines, such as blade deflection, could not be validated.

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The characteristics of helically deflected wind turbine wakes

Korb¹,

Asmuth²,

Ivanell³

2023

J. Fluid Mech.

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The helix approach is a new individual pitch control method to mitigate wake effects of wind turbines. Its name is derived from the helical shape of the wake caused by a rotating radial force exerted by the turbine. While its potential to increase power production has been shown in previous studies, the physics of the helical wake are not well understood to date. Open questions include whether the increased momentum in the wake stems from an enhanced wake mixing or from the wake deflection. Furthermore, its application to a row of more than two turbines has not been examined before. We study this approach in depth from both an analytical and numerical perspective. We examine large-eddy simulations (LES) of the wake of a single turbine and find that the helix approach exhibits both higher entrainment and notable deflection. As for the application to a row of turbines, we show that the phase difference between two helical wakes is independent of ambient turbulence. Examination of LES of a row of three turbines shows that power gains greatly depend on the phase difference between the helices. We find a maximum increase in the total power of approximately 10 % at a phase difference of $270^\circ$ . However, we do not optimise the phase difference any further. In summary, we provide a set of analytical tools for the examination of helical wakes, show why the helix approach is able to increase power production, and provide a method to extend it to a wind farm.

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Wind Turbine Response in Waked Inflow: A Modelling Benchmark Against Full-Scale Measurements

Cited by 3 publications

References 69 publications

Actuator line model using simplified force calculation methods

Actuator line model using simplified force calculation methods

Validation of a Lattice Boltzmann Solver Against Wind Turbine Response and Wake Measurements

The characteristics of helically deflected wind turbine wakes

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