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Open AccessArticle

Implications of Stably Stratified Atmospheric Boundary Layer Turbulence on the Near-Wake Structure of Wind Turbines

Department of Mechanical Engineering, University of Texas at San Antonio, 1 UTSA Circle, San Antonio, TX 78249, USA
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Energies 2014, 7(9), 5740-5763; https://doi.org/10.3390/en7095740
Received: 22 July 2014 / Revised: 21 August 2014 / Accepted: 26 August 2014 / Published: 2 September 2014
(This article belongs to the Special Issue Wind Turbines 2014)
Turbulence structure in the wake behind a full-scale horizontal-axis wind turbine under the influence of real-time atmospheric inflow conditions has been investigated using actuator-line-model based large-eddy-simulations. Precursor atmospheric boundary layer (ABL) simulations have been performed to obtain mean and turbulence states of the atmosphere under stable stratification subjected to two different cooling rates. Wind turbine simulations have revealed that, in addition to wind shear and ABL turbulence, height-varying wind angle and low-level jets are ABL metrics that influence the structure of the turbine wake. Increasing stability results in shallower boundary layers with stronger wind shear, steeper vertical wind angle gradients, lower turbulence, and suppressed vertical motions. A turbulent mixing layer forms downstream of the wind turbines, the strength and size of which decreases with increasing stability. Height dependent wind angle and turbulence are the ABL metrics influencing the lateral wake expansion. Further, ABL metrics strongly impact the evolution of tip and root vortices formed behind the rotor. Two factors play an important role in wake meandering: tip vortex merging due to the mutual inductance form of instability and the corresponding instability of the turbulent mixing layer. View Full-Text
Keywords: wind turbine; atmospheric boundary layer (ABL); wake effects; turbulence; mixing layer; tip and root vortices wind turbine; atmospheric boundary layer (ABL); wake effects; turbulence; mixing layer; tip and root vortices
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Bhaganagar, K.; Debnath, M. Implications of Stably Stratified Atmospheric Boundary Layer Turbulence on the Near-Wake Structure of Wind Turbines. Energies 2014, 7, 5740-5763.

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