Abstract
Velocity field measurements were carried out in the wake of a small straight-bladed vertical axis wind turbine (VAWT) by using an ultrasonic anemometer. The measurements of the V and W velocity components showed the downwash and the upwash, which proceeded toward the equator level and merged into the horizontal flow. The counter flow region was observed in the mainstream direction (U component). Expected increase in turbulent intensity caused by the dynamic-stall condition was not observed. Large thrust coefficients estimated from the deficit in the U velocity component suggested that the measured flow field may be highly different from the flow field assumed in the momentum theory.
