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Energies 2011, 4(11), 1916-1936; doi:10.3390/en4111916

Turbulent Flow Inside and Above a Wind Farm: A Wind-Tunnel Study

1
Saint Anthony Falls Laboratory, Department of Civil Engineering, University of Minnesota, Minneapolis, MN 55414, USA
2
Wind Engineering and Renewable Energy Laboratory (WIRE), School of Architecture, Civil and Environmental Engineering (ENAC), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
*
Author to whom correspondence should be addressed.
Received: 22 August 2011 / Revised: 8 October 2011 / Accepted: 28 October 2011 / Published: 8 November 2011
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Abstract

Wind-tunnel experiments were carried out to better understand boundary layer effects on the flow pattern inside and above a model wind farm under thermally neutral conditions. Cross-wire anemometry was used to characterize the turbulent flow structure at different locations around a 10 by 3 array of model wind turbines aligned with the mean flow and arranged in two different layouts (inter-turbine separation of 5 and 7 rotor diameters in the direction of the mean flow by 4 rotor diameters in its span). Results suggest that the turbulent flow can be characterized in two broad regions. The first, located below the turbine top tip height, has a direct effect on the performance of the turbines. In that region, the turbulent flow statistics appear to reach equilibrium as close as the third to fourth row of wind turbines for both layouts. In the second region, located right above the first one, the flow adjusts slowly. There, two layers can be identified: an internal boundary layer where the flow is affected by both the incoming wind and the wind turbines, and an equilibrium layer, where the flow is fully adjusted to the wind farm. An adjusted logarithmic velocity distribution is observed in the equilibrium layer starting from the sixth row of wind turbines. The effective surface roughness length induced by the wind farm is found to be higher than that predicted by some existing models. Momentum recovery and turbulence intensity are shown to be affected by the wind farm layout. Power spectra show that the signature of the tip vortices, in both streamwise and vertical velocity components, is highly affected by both the relative location in the wind farm and the wind farm layout. View Full-Text
Keywords: atmospheric boundary layer; turbulence; wind-tunnel experiment; wind farm; wind-turbine wake atmospheric boundary layer; turbulence; wind-tunnel experiment; wind farm; wind-turbine wake
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This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Chamorro, L.P.; Porté-Agel, F. Turbulent Flow Inside and Above a Wind Farm: A Wind-Tunnel Study. Energies 2011, 4, 1916-1936.

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