Abstract
Currently, vertical axis wind turbines (VAWT) are considered as an alternative technology to horizontal axis wind turbines in specific wind conditions, such as offshore farms. However, complex unsteady wake structures of VAWTs exert a significant influence on performance of wind turbines and wind farms. In the present study, instantaneous flow fields around and downstream of an innovative VAWT with inclined pitch axes are simulated by an actuator line model. Unsteady flow characteristics around the wind turbine with variations of azimuthal angles are discussed. Several fluid parameters are then evaluated on horizontal and vertical planes under conditions of various fold angles and incline angles. Results show that the total estimated wind energy in the shadow of the wind turbine with an incline angle of 30° and 150° is 4.6% higher than that with an incline angle of 90°. In this way, appropriate arrangements of wind turbines with various incline angles have the potential to obtain more power output in a wind farm.
Highlights
Modern wind turbines can be divided into horizontal axis wind turbines (HAWT) and vertical axis wind turbines (VAWT)
2.0°, 1.0°, 0.5°.6Results in Figure show thatcenter streamwise the center of the wake are slightly overpredicted with the velocities at the of thevelocities wake areatslightly overpredicted with the azimuthal increment of 2.0◦
The analysis mainly focuses on flow fields downstream in a range of x/D from −1 to 5, In the present study, flow fields around the wind turbine and downstream are acquired y/D from −1 to 1, and z/H from −1 to 1
Summary
Modern wind turbines can be divided into horizontal axis wind turbines (HAWT) and vertical axis wind turbines (VAWT). VAWTs perform competitive advantages over their counterparts [1], especially a faster wake recovery leading to a more compact turbine arrangement and higher power density of wind farms [2]. Strong blade–vortex interactions and complex unsteady wake structures are inherent attributes of VAWTs, which exert a significant influence on performance of wind turbines and wind farms [2,3,4]. Tescione et al [2] investigated asymmetric wake and vortex structures of a straight-bladed VAWT using stereoscopic particle image velocimetry (PIV). A more noticeable expansion of the wake is shown in the windward side on midspan horizontal planes. On vertical planes at several cross-stream locations, the wake contracts in the middle part but expanses at the edges with a wider divergence in the windward side. Rolin and Porte-Agel [6] illustrated boundary layer effect on the wake using
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