An Experimental Study on the Wake Development Behind a Yawed Model Wind Turbine
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Nowadays, wind turbines are usually optimized on an individual basis, and the entire windfarm is not considered as a whole. By yawing the upstream turbine, such that the wake isintentionally deflected away from the downstream turbine, the total amount of energy produced in the wind farm could be increased. In this study, experiments in the wind tunnel at the Norwegian University of Science and Technology have been conducted. The wakes behind a model wind turbine with a rotor diameter of 0.45m have been investigated in both non-yawed condition and with a yaw angle of 30. A comparison of the development of the two wakes is performed, as well as quantification of the deflected wake. It is shown that the wake behind the turbine in a non-yaw condition adopts a circular shape, while the wake behind the turbine in yawed condition has a more curled shape. The development of the velocity deficit of the two wakes is very similar. Three methods that estimates the wake center trajectory are applied to the measurements obtained from the experiment with the turbine in yaw. The results show that the quantfication of the wake deflection is strongly dependent of the method used. At last, an analytical model was implemented and compared with the methods. The model seems to over predict the deflection compared to one of the models that gives the most similar results to prior studies.