A Parametric Computational Fluid Dynamics (CFD) Study of In-Line Horizontal Axis Wind Turbines (HAWTs) with Yaw
Graduate Degree Type
School of Engineering
Dr. Wael Mokhtar
Dr. Lindsay Corneal
Dr. Mehmet Sozen
Because of the constant use of non-renewable fossil fuels, and the enormous impact they have on global warming and pollution, there has been a push to use more eco-friendly and renewable sources for power. One such form is wind power via turbines. The most common form, Horizontal Axis Wind Turbines (HAWTs), can generate massive amounts of power. However, they also have a serious flaw in their design. As the wind passes through the swept area of the blades and past the tower, it creates massive disturbances in the airflow. These disturbances are called a ‘wake’. When trying to create a wind farm with HAWTs, this wake must be accounted for as it can extend far beyond the initial turbine. This extension can lower wind speeds and therefore the power generated by a trailing turbine. However, recent testing has shown that inducing a positive yaw angle on a turbine can skew this wake. The skewing can be so extreme that if positive yaw is added to the leading of two in-line turbines, the system can have a positive increase in power generation. There has also been some disagreement on the actual percent increase seen in the overall generation. To help further the current understanding of this phenomenon, this thesis conducted steady-state CFD simulations on a 126-m diameter HAWT under various yaw and wind speed conditions. The testing done here determined that, while all turbines may see some wake redirection and an increase in trailing turbine power production because of the added yaw angle, the amount of benefit seen is turbine specific. Also revealed was a relationship between the leading turbine blade pitch angle and the amount of benefit the trailing turbine sees, if the pitch angle is corrected for by the amount of yaw added. As a recommendation for further study, more research must be done with yawed and pitched HAWTs to create a further understanding of this phenomenon.
Yates, North Alyster, "A Parametric Computational Fluid Dynamics (CFD) Study of In-Line Horizontal Axis Wind Turbines (HAWTs) with Yaw" (2021). Masters Theses. 1029.