Comparison of wind farm large eddy simulations using actuator disk and actuator line models with wind tunnel experiments

Stevens, Richard J. A. M.; Martínez‐Tossas, Luis A.; Meneveau, Charles

doi:10.1016/j.renene.2017.08.072

Cited by 213 publications

(166 citation statements)

References 41 publications

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“…In order to provide data to test predictions based on the proposed model in (2.4)-(2.7), numerical simulations of flow around a yawed actuator disk under uniform, laminar inflow are carried out using the pseudo-spectral code LESGO, which was validated in prior works (e.g. Calaf et al 2010;Stevens, Martínez & Meneveau 2018). A yawed actuator disk of diameter D is placed in a domain of length L x = 11.52D and cross-section size L y = L z = 5.76D using a total of 384 × 192 × 192 grid points.…”

Section: The Yawed Actuator Disk As An Elliptically Loaded Lifting Linementioning

confidence: 99%

Modelling yawed wind turbine wakes: a lifting line approach

2018

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Yawing wind turbines has emerged as an appealing method for wake deflection. However, the associated flow properties, including the magnitude of the transverse velocity associated with yawed turbines, are not fully understood. In this paper, we view a yawed turbine as a lifting surface with an elliptic distribution of transverse lift. Prandtl's lifting line theory provides predictions for the transverse velocity and magnitude of the shed counter-rotating vortex pair known to form downstream of the yawed turbine. The streamwise velocity deficit behind the turbine can then be obtained using classical momentum theory. This new model for the near-disk inviscid region of the flow is compared to numerical simulations and found to yield more accurate predictions of the initial transverse velocity and wake skewness angle than existing models. We use these predictions as initial conditions in a wake model of the downstream evolution of the turbulent wake flow and compare predicted wake deflection with measurements from wind tunnel experiments.

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Section: The Yawed Actuator Disk As An Elliptically Loaded Lifting Linementioning

confidence: 99%

Modelling yawed wind turbine wakes: a lifting line approach

2018

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“…We use a grid of 512 × 128 × 241 nodes, which is sufficient to capture the large-scale dynamics in the wind farm and similar to the grid resolution in previous studies, see for example other studies. 26,32,40 The turbines are modeled using an actuator disk model, 25,32,41 which has been shown to reasonably accurately capture wake profiles further downstream with a much lower computational cost 25,32,33,41,42 than an actuator line model. 43,44 Following previous studies, 25 we assume that the average turbine power output is equal to the mechanical energy loss in the fluid, ie, P = −FU d , where the overbar indicates The cases with smaller (D s = 100 m and z h = 100 m) and larger (D l = 150 m and z h = 120 m) turbines are denoted by normal and capital letters, respectively.…”

Section: Large Eddy Simulationmentioning

confidence: 99%

Large eddy simulations of the effect of vertical staggering in large wind farms

2018

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In order to study the effect of vertical staggering in large wind farms, large eddy simulations (LES) of large wind farms with a regular turbine layout aligned with the given wind direction were conducted. In the simulations, we varied the hub heights of consecutive downstream rows to create vertically staggered wind farms. We analysed the effect of streamwise and spanwise turbine spacing, the wind farm layout, the turbine rotor diameter, and hub height difference between consecutive downstream turbine rows on the average power output. We find that vertical staggering significantly increases the power production in the entrance region of large wind farms and is more effective when the streamwise turbine spacing and turbine diameter are smaller. Surprisingly, vertical staggering does not significantly improve the power production in the fully developed regime of the wind farm. The reason is that the downward vertical kinetic energy flux, which brings high velocity fluid from above the wind farm towards the hub height plane, does not increase due to vertical staggering. Thus, the shorter wind turbines are effectively sheltered from the atmospheric flow above the wind farm that supplies the energy, which limits the benefit of vertical staggering. In some cases, a vertically staggered wind farm even produced less power than the corresponding non vertically staggered reference wind farm. In such cases, the production of shorter turbines is significantly negatively impacted while the production of the taller turbine is only increased marginally.

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“…Using aerodynamic and geometric data of the blade as inputs, the ADMR accounts for the wake rotation and non-uniform force distribution on the wind turbine disk. Comparing to the LES results using the standard ADM, Wu and Porté-Agel [5] found that using the ADMR improves the prediction of the main wake flow statistics, such as the mean streamwise velocity and the turbulence intensity.The actuator line model (ALM) parameterisation, developed by Sørensen and Shen [6], was also applied in previous LES studies of wind turbine wakes (e.g., [7][8][9][10]). The ALM represents each blade of a wind turbine as a rotating line source of body forces and computes the corresponding blade-induced forces along the actuator line dynamically in the simulation.…”

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Large-Eddy Simulation of Yawed Wind-Turbine Wakes: Comparisons with Wind Tunnel Measurements and Analytical Wake Models

Lin

Porté‐Agel

2019

Energies

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In this study, we validated a wind-turbine parameterisation for large-eddy simulation (LES) of yawed wind-turbine wakes. The presented parameterisation is modified from the rotational actuator disk model (ADMR), which takes account of both thrust and tangential forces induced by a wind turbine based on the blade-element theory. LES results using the yawed ADMR were validated with wind-tunnel measurements of the wakes behind a stand-alone miniature wind turbine model with different yaw angles. Comparisons were also made with the predictions of analytical wake models. In general, LES results using the yawed ADMR are in good agreement with both wind-tunnel measurements and analytical wake models regarding wake deflections and spanwise profiles of the mean velocity deficit and the turbulence intensity. Moreover, the power output of the yawed wind turbine is directly computed from the tangential forces resolved by the yawed ADMR, in contrast with the indirect power estimation used in the standard actuator disk model. We found significant improvement in the power prediction from LES using the yawed ADMR over the simulations using the standard actuator disk without rotation, suggesting a good potential of the yawed ADMR to be applied in LES studies of active yaw control in wind farms.Energies 2019, 12, 4574 2 of 18 blade-resolved LES of ABL flows through wind turbines [3]. Therefore, most of the LES studies on wind turbine wakes represent the forces induced by wind turbines in ABL flows with various parameterisations.The standard actuator disk model (ADM) without rotation is the simplest wind turbine parameterisation, in which a wind turbine is modelled as a permeable disk with uniformly-distributed normal thrust forces applied on it [4]. A thrust coefficient C T is required by the standard ADM a priori to determine the magnitude of the thrust force. Wu and Porté-Agel [5] later proposed the rotational ADM parameterisation (ADMR), in which the wind turbine thrust and tangential forces are modelled by the blade-element theory. Using aerodynamic and geometric data of the blade as inputs, the ADMR accounts for the wake rotation and non-uniform force distribution on the wind turbine disk. Comparing to the LES results using the standard ADM, Wu and Porté-Agel [5] found that using the ADMR improves the prediction of the main wake flow statistics, such as the mean streamwise velocity and the turbulence intensity.The actuator line model (ALM) parameterisation, developed by Sørensen and Shen [6], was also applied in previous LES studies of wind turbine wakes (e.g., [7][8][9][10]). The ALM represents each blade of a wind turbine as a rotating line source of body forces and computes the corresponding blade-induced forces along the actuator line dynamically in the simulation. As the ALM computes the forces induced by each wind turbine blade, it can resolve more flow structures in the wake, such as tip vortices, than the standard ADM and the ADMR parameterisations. Using the ALM in LES also requires finer mesh resolution and time ste...

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Comparison of wind farm large eddy simulations using actuator disk and actuator line models with wind tunnel experiments

Cited by 213 publications

References 41 publications

Modelling yawed wind turbine wakes: a lifting line approach

Modelling yawed wind turbine wakes: a lifting line approach

Large eddy simulations of the effect of vertical staggering in large wind farms

Large-Eddy Simulation of Yawed Wind-Turbine Wakes: Comparisons with Wind Tunnel Measurements and Analytical Wake Models

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