Distribution of mean kinetic energy around an isolated wind turbine and a characteristic wind turbine of a very large wind farm

Cortina, Gerard; Calaf, Marc; Cal, Raúl Bayoán

doi:10.1103/physrevfluids.1.074402

Cited by 41 publications

(36 citation statements)

References 24 publications

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“…From the perspective of the streamtube control volume, there is a lateral (ū x u x u y ) as well as vertical (ū x u x u z ) kinetic energy flux. The lateral kinetic energy flux was also noted by Cortina et al [17] in wind farms with large spacing between turbines. In the wake of the turbine, some energy is removed from the mean through the production of turbulent kinetic energy (TKE).…”

Section: Domain (Xyz)supporting

confidence: 68%

“…Connections are drawn between the flow physics around individual wind turbines and wind farm performance trade-offs, which determine the optimal turbine thrust in the wind farm. This work is in the same vein as fundamental investigations of other variables affecting wind farm physics and performance, such as wind direction [15], turbine spacing [16], and atmospheric stability [11,17,18]. Especially as induction control strategies are being increasingly explored, understanding the flow physics of wind farms operating at different thrust coefficients becomes more important [19].…”

Section: Introductionmentioning

confidence: 95%

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Wind Turbine Performance in Very Large Wind Farms: Betz Analysis Revisited

West

Lele

2020

Energies

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The theoretical limit for wind turbine performance, the so-called Betz limit, arises from an inviscid, irrotational analysis of the streamtube around an actuator disk. In a wind farm in the atmospheric boundary layer, the physics are considerably more complex, encompassing shear, turbulent transport, and wakes from other turbines. In this study, the mean flow streamtube around a wind turbine in a wind farm is investigated with large eddy simulations of a periodic array of actuator disks in half-channel flow at a range of turbine thrust coefficients. Momentum and mean kinetic energy budgets are presented, connecting the energy budget for an individual turbine to the wind farm performance as a whole. It is noted that boundary layer turbulence plays a key role in wake recovery and energy conversion when considering the entire wind farm. The wind farm power coefficient is maximized when the work done by Reynolds stress on the periphery of the streamtube is maximized, although some mean kinetic energy is also dissipated into turbulence. This results in an optimal value of thrust coefficient lower than the traditional Betz result. The simulation results are used to evaluate Nishino’s model of infinite wind farms, and design trade-offs described by it are presented.

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Section: Domain (Xyz)supporting

confidence: 68%

Section: Introductionmentioning

confidence: 95%

Wind Turbine Performance in Very Large Wind Farms: Betz Analysis Revisited

West

Lele

2020

Energies

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“…b, Plot of the vertical, spanwise, and total wake modulation contributions to energy flux through a wake cross-section, normalized by the cube of the incoming velocity. The dark gray region indicates the time period where the turbine is operating in region 3, light gray in region 2.5, and white in region 2. c, Plot of dynamic wake modulation contributions to energy flux, normalized by the total flux per unit area in the vertical and spanwise directions reported by Cortina et al (2016) for an isolated wind turbine.…”

Section: Influence On Wake Recoverymentioning

confidence: 99%

Dynamic wake modulation induced by utility-scale wind turbine operation

Abraham

Hong

2020

Applied Energy

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Understanding wind turbine wake mixing and recovery is critical for improving the power generation and structural stability of downwind turbines in a wind farm. In the field, where incoming flow and turbine operation are constantly changing, wake recovery can be significantly influenced by dynamic wake modulation, which has not yet been explored. Here we present the first investigation of dynamic wake modulation in the near wake of a utility-scale turbine and quantify its relationship with changing conditions. This investigation is enabled using novel super-large-scale flow visualization with natural snowfall, providing unprecedented spatiotemporal resolution to resolve instantaneous changes of the wake envelope. These measurements reveal the significant influence of dynamic wake modulation on wake recovery. Further, our study uncovers the direct connection of dynamic wake modulation with operational parameters readily available to the turbine, paving the way for more precise wake prediction and control under field conditions for wind farm optimization.

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“…Yang et al developed a numerical approach to simulate the interaction of terrain‐induced turbulence with wind turbines sited in a large wind farm over complex terrain. Recently, a LES study performed by Cortina et al indicated that the recovery of mean kinetic energy around a characteristic wind turbine in a very large wind farm is dominated by the vertical flux. While a number of numerical and theoretical investigations have been performed for the development of wake models to predict flow characteristics inside wind farms, numerous onsite and wind tunnel experiments have also been conducted to evaluate the characteristics of turbulent flows and wake interferences among multiple turbines.…”

Section: Introductionmentioning

confidence: 99%