An Experimental Study on the Effects ofWinglets on the Wake and Performance of a ModelWind Turbine

Tobin, Nicolas; Hamed, Ali M.; Chamorro, Leonardo P.

doi:10.3390/en81011955

Cited by 50 publications

(36 citation statements)

References 24 publications

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“…The time‐averaged mean streamwise flow is generally seen to compare well for both blade tip configurations, while the only significant difference is a wider initial wake extension after the wingletted rotor. This finding agrees well with earlier observations by Shimizu et al, Johansen and Sørensen, Tobin et al, and Ostovan et al Ostovan et al also measured a wider wake extension and thicker mixing layer in the very near wake behind a three‐bladed wingletted rotor. A closer look into the fluctuating quantities in the wake revealed significant differences between the two investigated configurations.…”

Section: Discussionsupporting

confidence: 92%

“…An analysis of the streamwise velocity showed a wider wake extension for the wingletted configuration. Another PIV study of the wake up to

x false/ D

= 5 behind a significantly smaller rotor of

D

= 0.12 m with and without winglets was conducted by Tobin et al Their PIV study indicated an increased velocity deficit in the wake of the wingletted rotor. Although another downstream turbine, which was operated in the wake, was found to produce less power, the combined power of the two‐turbine array could be increased by the use of winglets.…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly, their results furthermore indicated a similar level of tip vortex circulation for the wingletted and baseline rotor. Although both instantaneous and phase‐averaged quantities were measured by Tobin et al, no analysis on the effect of winglets on the breakup mechanisms of the tip vortices was presented. The stability of the tip vortices in the wake of a wind turbine rotor is currently a widely discussed research topic (Sørensen, Sarmast et al, and Okulov et al).…”

Section: Introductionmentioning

confidence: 99%

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An experimental study on the effects of winglets on the tip vortex interaction in the near wake of a model wind turbine

et al. 2020

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An experimental study of the near wake up to four rotor diameters behind a model wind turbine rotor with two different wing tip configurations is performed. A straight-cut wing tip and a downstream-facing winglet shape are compared on the same two-bladed rotor operated at its design tip speed ratio. Phase-averaged measurements of the velocity vector are synchronized with the rotor position, visualizing the downstream location of tip vortex interaction for the two blade tip configurations. The mean streamwise velocity is found not to be strongly affected by the presence of winglet tip extensions, suggesting an insignificant effect of winglets on the time-averaged inflow conditions of a possible downstream wind turbine. An analysis of the phase-averaged vorticity, however, reveals a significantly earlier tip vortex interaction and breakup for the wingletted rotor. In contradistinction, the tip vortices formed behind the reference configuration are assessed to be more stable and start merging into larger turbulent structures significantly further downstream. These results indicate that an optimized winglet design can not only contribute to a higher energy extraction in a rotor's tip region but also can positively affect the wake's mean kinetic energy recovery by stimulating a faster tip vortex interaction. KEYWORDStip vortex, wake, wind energy, winglets 1 2.6%. Another study by Gaunaa and Johansen 7 showed a stronger positive effect on the power coefficient for downstream-facing winglets than

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Section: Discussionsupporting

confidence: 92%

“…An analysis of the streamwise velocity showed a wider wake extension for the wingletted configuration. Another PIV study of the wake up to

x false/ D

= 5 behind a significantly smaller rotor of

D

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An experimental study on the effects of winglets on the tip vortex interaction in the near wake of a model wind turbine

et al. 2020

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“…In the light of the above-mentioned benefits of wind tunnel experiments, they have been widely used in the wind-energy community to study wind turbines and their wakes (e.g., [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]). However, …”

Section: Introductionmentioning

confidence: 99%

A New Miniature Wind Turbine for Wind Tunnel Experiments. Part I: Design and Performance

Bastankhah

Porté‐Agel

2017

Energies

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Miniature wind turbines, employed in wind tunnel experiments to study the interaction of turbines with turbulent boundary layers, usually suffer from poor performance with respect to their large-scale counterparts in the field. Moreover, although wakes of wind turbines have been extensively examined in wind tunnel studies, the proper characterization of the performance of wind turbines has received relatively less attention. In this regard, the present study concerns the design and the performance analysis of a new three-bladed horizontal-axis miniature wind turbine with a rotor diameter of 15 cm. Due to its small size, this turbine, called WiRE-01, is particularly suitable for studies of wind farm flows and the interaction of the turbine with an incoming boundary-layer flow. Especial emphasis was placed on the accurate measurement of the mechanical power extracted by the miniature turbine from the incoming wind. In order to do so, a new setup was developed to directly measure the torque of the rotor shaft. Moreover, to provide a better understanding on the connection between the mechanical and electrical aspects of miniature wind turbines, the performance of three different direct-current (DC) generators was studied. It is found that electrical outputs of the tested generators can be used to provide a rather acceptable estimation of the mechanical input power. Force and power measurements showed that the thrust and power coefficients of the miniature turbine can reach 0.8 and 0.4, respectively, which are close to the ones of large-scale turbines in the field. In Part II of this study, the wake structure and dynamic flow characteristics are studied for the new miniature turbine immersed in a turbulent boundary-layer flow.

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“…The geometry of the representative rotor is based on a reference model turbine designed at Sandia National Laboratory [34,35]. A Precision Microdrive 112-001 Micro Core 12 mm Direct Current (DC) motor acted as the loading system, which resulted in a rated power P 0 ∼ 1 W [8,36]; additional information on the model turbine can be found in Tobin et al [37]. The two wind farm layouts consisted of aligned turbines with streamwise separation of S x = ∆x T /d T = 5 and 10, which shared the same spanwise separation of S y = ∆y/d T = 2.5.…”

Section: Methodsmentioning

confidence: 99%

On the Evolution of the Integral Time Scale within Wind Farms

et al. 2018

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A wind-tunnel investigation was carried out to characterize the spatial distribution of the integral time scale (T u ) within, and in the vicinity of, two model wind farms. The turbine arrays were placed over a rough wall and operated under high turbulence. The two layouts consisted of aligned units distinguished only by the streamwise spacing (∆x T ) between the devices, set at five and ten rotor diameters d T (or S x = ∆x T /d T = 5 and 10). They shared the same spanwise spacing between turbines of 2.5d T ; this resulted in arrays of 8 × 3 and 5 × 3 horizontal-axis turbines. Hotwire anemometry was used to characterize the instantaneous velocity at various vertical and transverse locations along the central column of the wind farms. Results show that T u was modulated by the wind farm layout. It was significantly reduced within the wind farms and right above them, where the internal boundary layer develops. The undisturbed levels above the wind farms were recovered only at ≈d T /2 above the top tip. This quantity appeared to reach adjusted values starting the fifth row of turbines in the S x = 5 wind farm, and earlier in the S x = 10 counterpart. Within the adjusted zone, the distribution of T u at hub height exhibited a negligible growth in the S x = 5 case; whereas it underwent a mild growth in the S x = 10 wind farm. In addition, the flow impinging the inner turbines exhibited T u /T u inc < 1, where T u inc is the integral time scale of the overall incoming flow. Specifically, T u → βT u inc at z = z hub , where β < 1 within standard layouts of wind farms, in particular β ≈ 0.5 and 0.7 for S x = 5 and 10.

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An Experimental Study on the Effects ofWinglets on the Wake and Performance of a ModelWind Turbine

Cited by 50 publications

References 24 publications

An experimental study on the effects of winglets on the tip vortex interaction in the near wake of a model wind turbine

An experimental study on the effects of winglets on the tip vortex interaction in the near wake of a model wind turbine

A New Miniature Wind Turbine for Wind Tunnel Experiments. Part I: Design and Performance

On the Evolution of the Integral Time Scale within Wind Farms

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