Experimental and theoretical study of wind turbine wakes in yawed conditions

By M. Bastankhah, Fernando Port'e-Agel. Journal of Fluid Mechanics, 2016

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This work is dedicated to systematically studying and predicting the wake characteristics of a yawed wind turbine immersed in a turbulent boundary layer. To achieve this goal, wind tunnel experiments were performed to characterize the wake of a horizontal-axis wind turbine model. A high-resolution stereoscopic particle image velocimetry system was used to measure the three velocity components in the turbine wake under different yaw angles and tip-speed ratios. Moreover, power and thrust measurements were carried out to analyse the performance of the wind turbine. These detailed wind tunnel measurements were then used to perform a budget study of the continuity and Reynolds-averaged Navier–Stokes equations for the wake of a yawed turbine. This theoretical analysis revealed some notable features of the wakes of yawed turbines, such as the asymmetric distribution of the wake skew angle with respect to the wake centre. Under highly yawed conditions, the formation of a counter-rotating vortex pair in the wake cross-section as well as the vertical displacement of the wake centre were shown and analysed. Finally, this study enabled us to develop general governing equations upon which a simple and computationally inexpensive analytical model was built. The proposed model aims at predicting the wake deflection and the far-wake velocity distribution for yawed turbines. Comparisons of model predictions with the wind tunnel measurements show that this simple model can acceptably predict the velocity distribution in the far wake of a yawed turbine. Apart from the ability of the model to predict wake flows in yawed conditions, it can provide valuable physical insight on the behaviour of turbine wakes in this complex situation.

View Paper: https://www.semanticscholar.org/paper/41c1ce84949a0dfda8a3bbba93036f3f505150d7

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Citations in the corpus

Wind-Turbine and Wind-Farm Flows: A Review (2019, methodology): “Bastankhah and Porté-Agel (2016) later used the budget study of RANS equations to develop an analytical model that predicts the wake-flow distribution in yawed conditions.”
Modelling yawed wind turbine wakes: a lifting line approach (2018, methodology): “The measured thrust coefficients of the rotating turbine (depending on the yaw angle, as reported in Bastankhah & Porté-Agel (2016)) are used to set the initial velocity deficits δu0 and δv0 in the model.”