As a solution to the energy problem and the environmental problem, wind energy has attracted attentions. In wind farm, wind turbines installed downwind sometimes operate in the wake generated by wind turbines installed upwind. It brings about power output decrement and load fluctuation of wind turbine, directly concerning failure and fatigue damage of the wind turbine. In this study, the observation of wind field in the wake generated by wind turbine in field was performed. The wind speed in wake was observed by using ultrasonic anemometers installed vertically on a meteorological mast. The present paper shows the results about wind speed recovery and wind direction change in the wake. With high turbulence flow, the wind speed in the wake recovers in short distance. It is because that high turbulence stimulates mixing at boundary of wake.
