An experimental and numerical study of the vortex structure in the wake of a wind turbine

Whale, Jonathan; Anderson, C.G.; Bareiß, Rainer; Wagner, Siegfried

doi:10.1016/s0167-6105(98)00201-3

Cited by 152 publications

(88 citation statements)

References 4 publications

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“…Fish must use more energy to swim in flow with streamwise vortices, which are shed off both rough elements on a streambed (Roy et al, 2004) and man-made devices like turbines and propellers (Whale et al, 2000), likely because they swim less steadily and move their pectoral fins in an unusual asymmetric way. The additional energy required is relatively low on average (6% over baseline swimming costs), but can be dramatically higher for certain individuals (up to an 82% increase).…”

Section: Discussionmentioning

confidence: 99%

Streamwise vortices destabilize swimming bluegill sunfish (Lepomis macrochirus)

Maia

Sheltzer

Tytell

2015

Journal of Experimental Biology

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In their natural environment, fish must swim stably through unsteady flows and vortices, including vertical vortices, typically shed by posts in a flow, horizontal cross-flow vortices, often produced by a step or a waterfall in a stream, and streamwise vortices, where the axis of rotation is aligned with the direction of the flow. Streamwise vortices are commonly shed by bluff bodies in streams and by ships' propellers and axial turbines, but we know little about their effects on fish. Here, we describe how bluegill sunfish use more energy and are destabilized more often in flow with strong streamwise vorticity. The vortices were created inside a sealed flow tank by an array of four turbines with similar diameter to the experimental fish. We measured oxygen consumption for seven sunfish swimming at 1.5 body lengths (BL) s −1 with the turbines rotating at 2 Hz and with the turbines off (control). Simultaneously, we filmed the fish ventrally and recorded the fraction of time spent maneuvering side-to-side and accelerating forward. Separately, we also recorded lateral and ventral video for a combination of swimming speeds (0.5, 1.5 and 2.5 BL s −1 ) and turbine speeds (0, 1, 2 and 3 Hz), immediately after turning the turbines on and 10 min later to test for accommodation. Bluegill sunfish are negatively affected by streamwise vorticity. Spills (loss of heading), maneuvers and accelerations were more frequent when the turbines were on than in the control treatment. These unsteady behaviors, particularly acceleration, correlated with an increase in oxygen consumption in the vortex flow. Bluegill sunfish are generally fast to recover from roll perturbations and do so by moving their pectoral fins. The frequency of spills decreased after the turbines had run for 10 min, but was still markedly higher than in the control, showing that fish partially adapt to streamwise vorticity, but not completely. Coping with streamwise vorticity may be an important energetic cost for stream fishes or migratory fishes.

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Section: Discussionmentioning

confidence: 99%

Streamwise vortices destabilize swimming bluegill sunfish (Lepomis macrochirus)

Maia

Sheltzer

Tytell

2015

Journal of Experimental Biology

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“…The nacelle was designed for minimising its effect on the flow: the ratio rotor-to-nacelle area is less than 6%. The studies of Whale et al (2000) have demonstrated that the wake exhibits a low dependency on the Reynolds number, comparing experimental measurements in the wake of a small wind-turbine with a chord-based Reynolds number ranging from 6400 to 16 000 with the results from an inviscid vortex code, representative of an infinite Reynolds number. The comparison shows a weak sensitivity to Reynolds number on the fundamental behaviour of the helical vortex wake, because the numerical results are fully comparable with the experimental ones.…”

Section: B Wind-turbine Modelmentioning

confidence: 99%

Experimental comparison of a wind-turbine and of an actuator-disc near wake

Lignarolo

Ragni

Ferreira

et al. 2016

Journal of Renewable and Sustainable Energy

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The actuator disc (AD) model is commonly used to simplify the simulation of horizontal-axis wind-turbine aerodynamics. The limitations of this approach in reproducing the wake losses in wind farm simulations have been proven by a previous research. The present study is aimed at providing an experimental analysis of the near-wake turbulent flow of a wind turbine (WT) and a porous disc, emulating the actuator disc numerical model. The general purpose is to highlight the similarities and to quantify the differences of the two models in the near-wake region, characterised by the largest discrepancies. The velocity fields in the wake of a wind turbine model and a porous disc (emulation of the actuator disc numerical model) have been measured in a wind tunnel using stereo particle image velocimetry. The study has been conducted at low turbulence intensity in order to separate the problems of the flow mixing caused by the external turbulence and the one caused by the turbulence induced directly by the AD or the WT presence. The analysis, as such, showed the intrinsic differences and similarities between the flows in the two wakes, solely due to the wake-induced flow, with no influence of external flow fluctuations. The data analysis provided the time-average three-component velocity and turbulence intensity fields, pressure fields, rotor and disc loading, vorticity fields, stagnation enthalpy distribution, and mean-flow kinetic-energy fluxes in the shear layer at the border of the wake. The properties have been compared in the wakes of the two models. Even in the absence of turbulence, the results show a good match in the thrust and energy coefficient, velocity, pressure, and enthalpy fields between wind turbine and actuator disc. However, the results show a different turbulence intensity and turbulent mixing. The results suggest the possibility to extend the use of the actuator disc model in numerical simulation until the very near wake, provided that the turbulent mixing is correctly represented.

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“…7,8 Also, the wake structure of a single wind turbine is a fairly well explored topic, [9][10][11][12][13][14][15][16][17][18] together with superposition effects of a finite number of wakes and their mutual interactions. [19][20][21][22][23][24][25] Pioneering works of Lissaman 26 and later Frandsen 25 led the way for understanding and modeling of an "infinite," or fully developed, array of wind turbines.…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulation study of scalar transport in fully developed wind-turbine array boundary layers

2011

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Mechanical stability of ordered droplet packings in microfluidic channels Appl. Phys. Lett. 99, 244104 (2011) Numerical investigation and evaluation of optimum hydrodynamic performance of a horizontal axis hydrokinetic turbine J. Wind harvesting is fast becoming an important alternative source of energy. As wind farms become larger, they begin to attain scales at which two-way interactions with the atmospheric boundary layer (ABL) must be taken into account. Several studies have shown that there is a quantifiable effect of wind farms on the local meteorology, mainly through changes in the land-atmosphere fluxes of heat and moisture. In particular, the observed trends suggest that wind farms increase fluxes at the surface and this could be due to increased turbulence in the wakes. Conversely, simulations and laboratory experiments show that underneath wind farms, the friction velocity is decreased due to extraction of momentum by the wind turbines, a factor that could decrease scalar fluxes at the surface. In order to study this issue in more detail, a suite of large eddy simulations of an infinite (fully developed) wind turbine array boundary layer, including scalar transport from the ground surface without stratification, is performed. Results show an overall increase in the scalar fluxes of about 10%-15% when wind turbines are present in the ABL, and that the increase does not strongly depend upon wind farm loading as described by the turbines' thrust coefficient and the wind turbines spacings. A single-column analysis including scalar transport shows that the presence of wind farms can be expected to increase slightly the scalar transport from the bottom surface and that this slight increase is due to a delicate balance between two strong opposing trends.

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An experimental and numerical study of the vortex structure in the wake of a wind turbine

Cited by 152 publications

References 4 publications

Streamwise vortices destabilize swimming bluegill sunfish (Lepomis macrochirus)

Streamwise vortices destabilize swimming bluegill sunfish (Lepomis macrochirus)

Experimental comparison of a wind-turbine and of an actuator-disc near wake

Large eddy simulation study of scalar transport in fully developed wind-turbine array boundary layers

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