Researchers from the University of Science and Technology of China, including Yu Tu, Kai Zhang, Zhaolong Han, Dai Zhou, and Onur Bilgen, have conducted a study to better understand how yaw control can improve the efficiency of wind farms. Their work, titled “Aerodynamic characterization of two tandem wind turbines under yaw misalignment control using actuator line model,” was published in the journal Renewable Energy.
Wind farms often face efficiency challenges due to wake effects, where the turbulence created by upstream turbines can disrupt the airflow to downstream turbines. To mitigate this issue, the researchers used a method called actuator line modeling (ALM) to simulate the airflow over two tandem wind turbines positioned at distances of 3 to 7 rotor diameters apart. They varied the yaw angle of the upstream rotor from 0 to 50 degrees to observe its impact on the overall performance of the wind turbines.
The study found that as the yaw angle of the upstream turbine increased, the power generated by the downstream turbine also increased. This compensated for the power loss experienced by the upstream turbine, resulting in a higher total power output for both turbines compared to when no yaw control was applied. The maximum power output was achieved when the upstream wake was redirected away from the downstream rotor plane.
The researchers also observed a secondary steering phenomenon, where the wake behind the downstream rotor was redirected from the centerline. Using the actuator line model, they were able to capture unsteady aerodynamic characteristics that lower-fidelity models might miss. For the upstream rotor, yaw misalignment caused time-varying changes in the local angle of attack on the blade, leading to unsteady loading. The downstream rotor, partially submerged in the deflected wake of the yawed upstream rotor, experienced cyclic loading as the blade revolved into and out of the wake deficit. This resulted in even stronger fluctuations in aerodynamic loads compared to the upstream rotor.
The insights gained from this study can aid in the design of collective yaw control strategies for wind farms. By understanding the aerodynamic performance, wake profiles, and unsteady characteristics of yaw control, wind farm operators can optimize their turbine configurations to maximize efficiency and reduce fatigue damage associated with yaw misalignment. This research provides a valuable foundation for improving the overall performance and longevity of wind farms.
This article is based on research available at arXiv.