Development and Testing of a Fairing for a Wind Turbine Tower

The average rated power of wind turbines is growing yearly. As the size of the average wind turbine increases, new designs are needed to handle the increased loads, and some of these designs may require a downwind configuration. Such a configuration requires the wind turbine blades to pass through the turbulent wake of the tower, and this can lead to blade fatigue and, eventually, blade failure. Implementing an aerodynamic fairing around the tower can substantially reduce the effects of the wake on the blades. Ideally, the fairing will meet four objectives: 1) low drag, 2) a short trailing edge relative to the tower center, 3) a moment that results in self-alignment about the tower center, and 4) no large adverse pressure gradients. The prospective fairing designs were analyzed computationally using XFOIL. The computational software was unable to accurately predict flow separation at high Reynolds numbers, so experiments were conducted in a water channel to analyze two airfoils of interest. Flow visualization was used to explore the ability of the airfoils to delay flow separation and particle image velocimetry (PIV) was used to analyze the wake of the airfoils at several angles of attack. Restrictions to the flow speed and model sizes prevented the experimental Reynolds number from being matched with the full-scale Reynolds number. To properly determine the best fairing design, experiments must be conducted at a higher Reynolds number.