| 1. |
- Helvig, Sanne de Jong, et al.
(författare)
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A comparison of lab-scale free rotating wind turbines and actuator disks
- 2021
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105 .- 1872-8197. ; 209
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Tidskriftsartikel (refereegranskat)abstract
- Planar particle image velocimetry was conducted upstream and in the near-wake of a lab-scale free-rotating wind turbine model and compared to several actuator disks with the same dimensions. The Reynolds number of the incoming flow is order 10(4). Actuator disks with different designs and solidities were tested, and the process of actuator disk selection is explicitly shown. The drag, mean velocity and mean vorticity in the wake of the disks were compared to that of the rotating model. For the disk that was the best match, the Reynolds stresses and swirling strength are also presented. The instantaneous swirling strength illustrated that despite similar mean fields, the instantaneous phenomena were significantly different. Distinct tip vortices were present in the wake of the rotating model but were absent from the wake of the actuator disk. Proper orthogonal decomposition was used to further investigate the underlying phenomena in the two flows, again demonstrating the importance of tip vortices when studying the rotating model and the lack of such distinct vortices when using the actuator disk. Hence, despite well-matched mean characteristics, the instantaneous structures in the two flows remain distinct.
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| 2. |
- Vinnes, Magnus K., et al.
(författare)
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The flow in the induction and entrance regions of lab-scale wind farms
- 2023
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Ingår i: Wind Energy. - : John Wiley & Sons. - 1095-4244 .- 1099-1824. ; 26:10, s. 1049-1065
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Tidskriftsartikel (refereegranskat)abstract
- With the increasing demand for wind energy, it is important to be able to understand and predict the available wind resources. To that end, the present wind tunnel study addresses the flow in the induction and entrance region of wind farms through particle image velocimetry, with focus on differences between actuator disks and two-bladed rotating wind turbine models. Both staggered and aligned farm layouts are examined for three different incoming wind directions. For each layout, 69 disks or turbines are used, and the field of view ranges from 12 rotor diameters upstream of the farms to 8 diameters downstream of the first row. The results show that the induction, or blockage effect, is higher for the disks, even though the thrust (or drag) coefficient is the same. In contrast, the wake is stronger downstream of the turbines. The orientation and layout of the farm do not have a major impact on the results. Modal decomposition of the flow shows that the flow structure similarity between the disk and turbines improves downstream of the second row of wake generating objects, indicating that the substitution of wind turbines by actuator disks is more appropriate for wind farms than for the investigation of single wakes.
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