Laboratory investigation of the near and intermediate wake of a wind turbine at very high Reynolds numbers

Piqué, Alexander; Miller, Mark A.; Hultmark, Marcus

doi:10.1007/s00348-022-03455-0

Cited by 5 publications

(3 citation statements)

References 43 publications

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“…Research efforts aimed at characterizing the behaviour of wind turbines are complicated by the increasingly large dimensions of modern rotors, which make high-fidelity numerical simulations prohibitively expensive and limit most laboratory experiments to reduced Reynolds numbers, with rare exceptions (e.g., [14]). This is an issue because, at low Reynolds numbers, the performance of a wind turbine is Reynolds-number-dependent [15], even after the main flow statistics have reached Reynolds number independence [16], with small-scale turbines generally performing worse than their full-scale counterparts [17,18].…”

Section: Introductionmentioning

confidence: 99%

An Experimental Study on a Wind Turbine Rotor Affected by Pitch Imbalance

et al. 2022

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An experimental and numerical investigation about the pitch imbalance effect on a wind turbine model is performed. The characterization of the power losses and loads generated on a small-scale model and the validation of an analytical framework for the performance of unbalanced rotors are proposed. Starting from the optimal collective pitch assessment (performed to identify the condition with the maximum power coefficient), the pitch of just one blade was systematically changed: it is seen that the presence of a pitch misalignment is associated with a degradation of the turbine performance, visible both from experiments and from Blade Element Momentum (BEM) calculations (modified to account for the load asymmetry). Up to 30% power losses and a 15% thrust increase are achievable when an imbalanced rotor operates at tip speed ratios around five, clearly highlighting the importance of avoiding this phenomenon when dealing with industrial applications. The numerical model predicts this result within 5% accuracy. Additional numerical simulations showed that, away from the optimal collective pitch, the blade imbalance can provide a power increase or a power decrease with respect to the balanced case, suggesting how an operator can maximise the production of an unbalanced rotor. An analysis of the axial and lateral forces showed a sensitivity of the loads’ standard deviation when imbalance is present. An increase of the lateral loads was observed in all unbalanced cases.

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Section: Introductionmentioning

confidence: 99%

An Experimental Study on a Wind Turbine Rotor Affected by Pitch Imbalance

et al. 2022

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“…Abraham et al [15] experimentally investigated the effectiveness of different types of rotor asymmetries in wake vortex evolution and proposed a method to mitigate downstream wake effects. Piqué et al [16] measured the variation in Reynolds number on the velocity field at different flow positions of a horizontal axis wind turbine in wind tunnel experiments. Gao et al [17] validated the accuracy of the derived wake model through wind tunnel scale experiments and compared it with measurements from actual wind farms.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Wake Evolution under Vertical Staggered Arrangement of Wind Turbines of Different Sizes

Zhang,

Feng,

Zhao

et al. 2024

JMSE

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During the expansion of a wind farm, the strategic placement of wind turbines can significantly improve wind energy utilization. This study investigates the evolution of wake turbulence in a wind farm after introducing smaller wind turbines within the gaps between larger ones, focusing on aspects such as wind speed, turbulence intensity, and turbulence integral length scale. The flow field conditions are described using parameters like turbulence critical length and power spectral density, as determined through wind tunnel experiments. In these experiments, a single large wind turbine model and nine smaller wind turbine models were used to create a small wind farm unit, and pressure distribution behind the wind turbines was measured under various operating conditions. The results indicate that downstream wind speed deficits intensify as the number of small wind turbines in operation increases. The impact of these smaller turbines varies with height, with a relatively minor effect on the upper blade tip and increasingly adverse effects as you move from the upper blade tip to the lower blade tip. Through an analysis of power spectral density, the contribution of vortex motion to wake turbulence kinetic energy is further quantified. In the far wake region, the number of small wind turbines has a relatively small impact on wind speed fluctuations.

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“…The paper [18] compares the main literature on experimental and theoretical studies regarding atmospheric boundary layers' wind turbines' interaction in specified terrains (in specified wind farms), and the impact on the feasibility of relevant wind farms. In [19], the authors show a very simple case study when using a VAWT that is placed on a flat and homogeneous ground. A further work [20] presents the analysis of the interaction process between all the turbines in a wind farm in the function of the wake effect.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Wind Turbine Distances Using a Novel Techno-Spatial Approach in Complex Wind Farm Terrains

2022

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Among the current challenges facing the energy sector is finding environmentally friendly and high-performance forms of energy generation. One such form of energy generation is from the wind. In addition to the fluctuations that cause changes in the generated energy, another factor that significantly affects the overall efficiency of wind farms is the distance between the turbines. In that context, a distance of at least three diameters (3D) onwards is necessary to enable a stable operation. This is more difficult to implement for mountainous terrain due to the terrain configuration’s influence, the turbine units’ positioning, and the mutual influence resulting from their position in the area under consideration. This work investigates the interdependence of the terrain features, the placement of ten turbines in different scenarios, and the impact on the overall efficiency of the wind farm. The place where the wind farm is considered is in Koznica, a mountainous area near Prishtina. An analysis has been carried out for two-diameter (2D), three-diameter (3D), and five-diameter (5D) turbine blade spacing for turbines with a rated power of 3.4 MW. The study considers placement in the following forms: Arc, I, L, M, and V. The results show that for 2D distance layout, the capacity factors for Arc, I, L, M, and V placements have the values: 32.9%, 29.8%, 31.1%, 30.6%, and 37.1%. For the 3D distance, according to these scenarios, the capacity factor values are: 29.9%, 30.8%, 30.4%, 29.3%, and 35.6%. For the longest distance, 5D, the capacity factor values are: 28.9%, 29.9%, 29.4%, 27.6%, and 30.6%. The value of the capacity factor for an optimal layout; is achieved at 39.3%.

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Laboratory investigation of the near and intermediate wake of a wind turbine at very high Reynolds numbers

Cited by 5 publications

References 43 publications

An Experimental Study on a Wind Turbine Rotor Affected by Pitch Imbalance

An Experimental Study on a Wind Turbine Rotor Affected by Pitch Imbalance

Experimental Study of Wake Evolution under Vertical Staggered Arrangement of Wind Turbines of Different Sizes

Analysis of Wind Turbine Distances Using a Novel Techno-Spatial Approach in Complex Wind Farm Terrains

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