A Measurement of the Three-Dimensional Near-Wake Velocity Field of a Model Horizontal-Axis Wind Turbine

摘要

The three-dimensional near-wake velocity field of a model horizontal-axis wind turbine (HAWT) has been measured, using a single slanted hot-wire probe. The primary aim of this paper was to document the formation and development of the three-dimensional wake. This task was done at five axial locations within four chord lengths of the blades over a range of tip speed ratios. The measurements of the mean velocity and turbulence were obtained from a stationary slanted hot-wire anemometer by the technique of phase-locked averaging. The results show that during the downstream development of the wake, the track of the wake centre forms a helical curve which rotation direction is opposite that of the rotor. The distribution of mean velocity behind the HAWT rotor reveals the expansion and decay of the three-dimensional wake. The shapes of the mean velocity distribution are similar along the blades span at the same downstream axial location. It is shown that the turbulence levels in the wake are relatively higher than those of in the non-wake region. Especially, the magnitude of circumferential component and radial component of turbulence intensity are higher than that of axial component of turbulence intensity in the wake region. These data can be taken to identify and better understand the physical attributes of the flow field as well as to aid the accurate prediction of the performance of HAWT.