Three-dimensional flow field around and downstream of a subscale model rotating vertical axis wind turbine

Ryan, Kevin; Coletti, Filippo; Elkins, Christopher J.; Dabiri, John O.; Eaton, John K.

doi:10.1007/s00348-016-2122-z

Cited by 59 publications

(61 citation statements)

References 19 publications

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“…Rolin et al [12] employed a stereo-PIV technique and observed two pairs of asymmetrical-counter-rotating vortices at the horizontal edges of the wake as a result of a variation in cross-flow momentum. Analogously, Ryan et al [13] observed that the strength of this pair of vortices is directly related to the turbine's rotational speed.…”

Section: Introductionmentioning

confidence: 78%

Three-dimensionality of the wake recovery behind a vertical axis turbine

et al. 2019

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The wake recovery downstream of a vertical axis turbine operating in a turbulent channel flow is investigated via detailed velocity measurements using an Acoustic Doppler Velocimeter. Three distinct wake regions are identified: (i) a near-wake region which extends until two rotor diameters (2D) downstream and characterised by a low-momentum area isolated from the ambient flow and the presence of energetic dynamic stall vortices; (ii) a transition region (2D-5D), characterised by a fast momentum recovery, high turbulence intensity levels and vertical expansion of the wake; and (iii) a far-wake region beyond 5D where the velocity recovers to approximately 95% of the free-stream velocity. Albeit the wake deficit recovery is mostly accomplished at 5D behind the turbine, rotorinduced effects are still present beyond 10D as indicated by high-order flow statistics, such as high velocity fluctuations and flow skewness. Analysis of the streamwise momentum budget reveal that advection terms are mainly responsible for momentum replenishment through most of the wake and turbulent transport terms play only a minor role. This study evidences the anisotropic nature of the turbulence and asymmetry of the flow in horizontal, vertical and cross-sectional planes downstream of the vertical axis turbine.

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Section: Introductionmentioning

confidence: 78%

Three-dimensionality of the wake recovery behind a vertical axis turbine

et al. 2019

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“…Much work, including field-scale measurements [6][7][8][9], laboratory experiments [10][11][12][13][14][15][16][17], and numerical simulations [18][19][20][21][22][23][24][25] has been done recently to study the aerodynamics of VAWTs. In the following, a brief review of the most recent studies related to fluid mechanics of VAWTs is provided.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Modeling of Vertical-Axis Wind Turbine Wakes

Abkar

2018

Energies

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In this work, two different theoretical models for predicting the wind velocity downwind of an H-rotor vertical-axis wind turbine are presented. The first model uses mass conservation together with the momentum theory and assumes a top-hat distribution for the wind velocity deficit. The second model considers a two-dimensional Gaussian shape for the velocity defect and satisfies mass continuity and the momentum balance. Both approaches are consistent with the existing and widely-used theoretical wake models for horizontal-axis wind turbines and, thus, can be implemented in the current numerical codes utilized for optimization and real-time applications. To assess and compare the two proposed models, we use large eddy simulation as well as field measurement data of vertical-axis wind turbine wakes. The results show that, although both models are generally capable of predicting the velocity defect, the prediction from the Gaussian-based wake model is more accurate compared to the top-hat counterpart. This is mainly related to the consistency of the assumptions used in the Gaussian-based wake model with the physics of the turbulent wake development downwind of the turbine.

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“…Having a thorough understanding of VAWT wakes is especially crucial in designing VAWT wind farms, where downstream turbines can potentially be located in the wake of upstream ones, and consequently, the performance of the whole wind farm could be significantly affected by the wake flow characteristics. Among the experimental works investigating VAWT wakes, one can find a relatively larger number of studies that have focused only on the near wake region (e.g., [2][3][4][5]), compared to those that have considered also the far wake region (e.g., [6][7][8]). Nevertheless, from a wind farm design point of view, it is the far wake behavior of the flow that has more relevance and importance.…”

Section: Introductionmentioning

confidence: 99%

A Large-Eddy Simulation Study of Vertical Axis Wind Turbine Wakes in the Atmospheric Boundary Layer

Shamsoddin

Porté‐Agel

2016

Energies

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Abstract:In a future sustainable energy vision, in which diversified conversion of renewable energies is essential, vertical axis wind turbines (VAWTs) exhibit some potential as a reliable means of wind energy extraction alongside conventional horizontal axis wind turbines (HAWTs). Nevertheless, there is currently a relative shortage of scientific, academic and technical investigations of VAWTs as compared to HAWTs. Having this in mind, in this work, we aim to, for the first time, study the wake of a single VAWT placed in the atmospheric boundary layer using large-eddy simulation (LES). To do this, we use a previously-validated LES framework in which an actuator line model (ALM) is incorporated. First, for a typical three-and straight-bladed 1-MW VAWT design, the variation of the power coefficient with both the chord length of the blades and the tip-speed ratio is analyzed by performing 117 simulations using LES-ALM. The optimum combination of solidity (defined as Nc/R, where N is the number of blades, c is the chord length and R is the rotor radius) and tip-speed ratio is found to be 0.18 and 4.5, respectively. Subsequently, the wake of a VAWT with these optimum specifications is thoroughly examined by showing different relevant mean and turbulence wake flow statistics. It is found that for this case, the maximum velocity deficit at the equator height of the turbine occurs 2.7 rotor diameters downstream of the center of the turbine, and only after that point, the wake starts to recover. Moreover, it is observed that the maximum turbulence intensity (TI) at the equator height of the turbine occurs at a distance of about 3.8 rotor diameters downstream of the turbine. As we move towards the upper and lower edges of the turbine, the maximum TI (at a certain height) increases, and its location moves relatively closer to the turbine. Furthermore, whereas both TI and turbulent momentum flux fields show clear vertical asymmetries (with larger magnitudes at the upper wake edge compared to the ones at the lower edge), only slight lateral asymmetries were observed at the optimum tip-speed ratio for which the simulations were performed.

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Three-dimensional flow field around and downstream of a subscale model rotating vertical axis wind turbine

Cited by 59 publications

References 19 publications

Three-dimensionality of the wake recovery behind a vertical axis turbine

Three-dimensionality of the wake recovery behind a vertical axis turbine

Theoretical Modeling of Vertical-Axis Wind Turbine Wakes

A Large-Eddy Simulation Study of Vertical Axis Wind Turbine Wakes in the Atmospheric Boundary Layer

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