Clarification of influences of inflow conditions on wake of horizontal axis wind turbine

Abstract

In recent years, wind turbines are introduced in wind farms in which some wind turbines are concentrated. When wind turbines are built in contiguity with each other in wind farms, the flow passing through a wind turbine, which is called wake, may flow into other wind turbines. Wake is characterized by a large fluctuation of the wind speed and direction. Flow of wake into wind turbines causes decrease of power generation and increase of fatigue load on wind turbines. Therefore, in order to propose the best arrangement of wind turbines in wind farms, sufficient understanding of wake characteristics is required. Wake is significantly influenced by inflow conditions. Therefore, experimental investigations were carried out in a wind tunnel and the effects of various inflow conditions on wake were considered. From the experimental results, it was found that recovery of wind velocity and expansion of wake deficit area were promoted by turbulence of inflow generated by active turbulence grids. Wake center was deflected from the center line of wind turbine in yawed inflow. Wind shear of inflow generated by boundary layer generation device promoted horizontal expansion of wake deficit area. Also, wake velocity distribution was evaluated quantitatively by wake model using Gaussian function and it showed good approximation to wake distribution in downstream more than 3 times of the rotor diameter.