Implementation of a generalized actuator disk wind turbine model into the weather research and forecasting model for large-eddy simulation applications

Mirocha, Jeffrey D.; Kosović, Branko; Aitken, Matthew L.; Lundquist, Julie K.

doi:10.1063/1.4861061

Cited by 98 publications

(124 citation statements)

References 53 publications

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“…Moreover, after the evening transition, the hub-height wind-speed deficit persists for more than 15 km downwind, while the turbulence enhancement vanishes beyond 10 km downwind. In contrast to LES studies with constant atmospheric stratification (Churchfield et al 2012;Mirocha et al 2014Mirocha et al , 2015Abkar and Porté-Agel 2015;Vanderwende et al 2016a), the wake structure illustrated herein varies both temporally and spatially downwind of the wind farm. The turbine locations in these simulations, based on an actual wind farm, contribute to this variability.…”

Section: Discussionmentioning

confidence: 50%

“…GAD model results have indicated that turbine wakes expand more in the horizontal direction than vertically (Mirocha et al 2014). At a downwind distance of 6.5 times the rotor diameter (D), the flow experiences up to 25% wind-speed reduction in a weakly convective regime (Mirocha et al 2014). LES has also revealed that the wind-speed deficit extends further downwind, the turbulence generation decreases and the overall wake recovers more slowly in the stable PBL than in the unstable PBL (Abkar and Porté-Agel 2015;Bhaganagar and Debnath 2015;Mirocha et al 2015).…”

Section: Turbine-wake Simulationsmentioning

confidence: 90%

Section: Turbine-wake Simulationsmentioning

confidence: 99%

“…Comparisons of lidar measurements to large-eddy simulations (LES) with a generalized actuator disk (GAD) model in the Weather Research and Forecasting (WRF) model are capable of representing wake-deficit characteristics qualitatively (Mirocha et al 2014Aitken et al 2014b). GAD model results have indicated that turbine wakes expand more in the horizontal direction than vertically (Mirocha et al 2014).…”

Section: Turbine-wake Simulationsmentioning

confidence: 99%

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Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Lee

Lundquist

2017

Boundary-Layer Meteorol

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Wind-turbine-wake evolution during the evening transition introduces variability to wind-farm power production at a time of day typically characterized by high electricity demand. During the evening transition, the atmosphere evolves from an unstable to a stable regime, and vertical stratification of the wind profile develops as the residual planetary boundary layer decouples from the surface layer. The evolution of wind-turbine wakes during the evening transition is examined from two perspectives: wake observations from single turbines, and simulations of multiple turbine wakes using the mesoscale Weather Research and Forecasting (WRF) model. Throughout the evening transition, the wake's wind-speed deficit and turbulence enhancement are confined within the rotor layer when the atmospheric stability changes from unstable to stable. The height variations of maximum upwind-downwind differences of wind speed and turbulence intensity gradually decrease during the evening transition. After verifying the WRF-model-simulated upwind wind speed, wind direction and turbulent kinetic energy profiles with observations, the wind-farm-scale wake evolution during the evening transition is investigated using the WRF-model wind-farm parametrization scheme. As the evening progresses, due to the presence of the wind farm, the modelled hub-height wind-speed deficit monotonically increases, the relative turbulence enhancement at hub height grows by 50%, and the downwind surface sensible heat flux increases, reducing surface cooling. Overall, the intensifying wakes from upwind turbines respond to the evolving atmospheric boundary layer during the evening transition, and undermine the power production of downwind turbines in the evening.

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Section: Discussionmentioning

confidence: 50%

Section: Turbine-wake Simulationsmentioning

confidence: 90%

Section: Turbine-wake Simulationsmentioning

confidence: 99%

Section: Turbine-wake Simulationsmentioning

confidence: 99%

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Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Lee

Lundquist

2017

Boundary-Layer Meteorol

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“…This allows for better characterization of wake meandering and unsteady loads on turbines. Finally, wind plant modeling has also been improved through coupling to numerical weather prediction simulations (Fitch et al, 2012;Mirocha et al, 2014). Such simulations are able to incorporate synoptic-scale weather forcing and interactions between the surface, wind plant, and full atmospheric boundary layer.…”

Section: Wind Plant Flow Modelingmentioning

confidence: 99%

Optimization of wind plant layouts using an adjoint approach

et al. 2017

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Abstract. Using adjoint optimization and three-dimensional steady-state Reynolds-averaged Navier-Stokes (RANS) simulations, we present a new gradient-based approach for optimally siting wind turbines within utilityscale wind plants. By solving the adjoint equations of the flow model, the gradients needed for optimization are found at a cost that is independent of the number of control variables, thereby permitting optimization of large wind plants with many turbine locations. Moreover, compared to the common approach of superimposing prescribed wake deficits onto linearized flow models, the computational efficiency of the adjoint approach allows the use of higher-fidelity RANS flow models which can capture nonlinear turbulent flow physics within a wind plant. The steady-state RANS flow model is implemented in the Python finite-element package FEniCS and the derivation and solution of the discrete adjoint equations are automated within the dolfin-adjoint framework. Gradient-based optimization of wind turbine locations is demonstrated for idealized test cases that reveal new optimization heuristics such as rotational symmetry, local speedups, and nonlinear wake curvature effects. Layout optimization is also demonstrated on more complex wind rose shapes, including a full annual energy production (AEP) layout optimization over 36 inflow directions and 5 wind speed bins.

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Toward understanding the physical link between turbines and microclimate impacts from in situ measurements in a large wind farm

et al. 2016

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Recent wind farm studies have revealed elevated nighttime surface temperatures but have not validated physical mechanisms that create the observed effects. We report measurements of concurrent differences in surface wind speed, temperature, fluxes, and turbulence upwind and downwind of two turbine lines at the windward edge of a utility‐scale wind farm. On the basis of these measurements, we offer a conceptual model based on physical mechanisms of how wind farms affect their own microclimate. Periods of documented curtailment and zero‐power production of the wind farm offer useful opportunities to rigorously evaluate the microclimate impact of both stationary and operating turbines. During an 80 min nighttime wind farm curtailment, we measured abrupt and large changes in turbulent fluxes of momentum and heat leeward of the turbines. At night, wind speed decreases in the near wake when turbines are off but abruptly increases when turbine operation is resumed. Our measurements are compared with Moderate Resolution Imaging Spectroradiometer Terra and Aqua satellite measurements reporting wind farms to have higher nighttime surface temperatures. We demonstrate that turbine wakes modify surface fluxes continuously through the night, with similar magnitudes during the Terra and Aqua transit periods. Cooling occurs in the near wake and warming in the far wake when turbines are on, but cooling is negligible when turbines are off. Wind speed and surface stratification have a regulating effect of enhancing or decreasing the impact on surface microclimate due to turbine wake effects.

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Implementation of a generalized actuator disk wind turbine model into the weather research and forecasting model for large-eddy simulation applications

Cited by 98 publications

References 53 publications

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Optimization of wind plant layouts using an adjoint approach

Toward understanding the physical link between turbines and microclimate impacts from in situ measurements in a large wind farm

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