Turbulent Axisymmetric Wake with Rotation
Wind energy is becoming an increasingly important source of non-fossil electric energy. In 2014 wind energy provided 4.4% of all electricity in the United States, compared to only 0.1% in 2000 . In wind farms, the turbulent wake flow created by upwind turbines affects the efficiency (energy production) of the downwind turbines and also causes fatigue loading on the rotors, which decreases the mechanical life of the system. A detailed understanding of this turbulent wake flow is necessary for designing turbine arrays.
The wake of realistically scaled model wind turbine was measured in the UNH Flow Physics Facility, a large boundary layer wind tunnel, using pitot tubes and laser Doppler velocimetry (LDV). Wake profiles were measured starting close behind the rotor to 20 turbine diameters downstream, in the free stream and in the turbulent boundary layer. After tip and hub vortices break down, the wake becomes more uniform as it gradually recovers and the amount of turbulence slowly decreases. By exploring the velocity profiles it can be examined whether the wake becomes self-similar, which can be used to predict wake behavior. The results from this research can help improve the array spacing to increase energy output and reduce the turbulent loads on the turbines.
Available from the National Sea Grant Library (use NHU number to search) or NH Sea Grant
- Turbulent axisymmetric wake with rotation (2014). Austin Trombino, Brian Donahue and Sheldon Baker. Advisor: Martin Wosnik.