Diagonal inflow effect on the wake characteristics of a horizontal axis wind turbine with Gaussian model and field measurements

This paper investigates the diagonal inflow effect on the wake characteristics of a HAWT (Horizontal Axis Wind Turbine) in a wind farm. In this study, a HAWT with the generator capacity of 30 kW and the rotor diameter of 10.0 m is used. Firstly, the effect of pitch angle on the power and thrust performances of wind turbine are investigated through field experiment. On this basis, the wake characteristics of the HAWT are examined with different wind directions and pitch angles. The velocity field is measured by the ultrasonic anemometers, the three-cup type anemometer and the wind vane. Finally, the annual power generation of the downstream wind turbine is predicted by different Gaussian models. As a result, the maximum power coefficients C-p are 0.31, 0.33 and 0.27, corresponding to the tip speed ratios lambda = 7.5, 7.4 and 6.8 and the pitch angles beta = 0 degrees, 2 degrees and 4 degrees, respectively. The standard deviations of wind direction are divided into four regions between sigma(theta) = 5 degrees and 20 degrees. The maximum deficit values of the wake velocity decreases from 0.27 to 0.16, and the full wake widths at half maximum D r increases from 1.35 to 1.71 with sigma(theta) increasing from 5 degrees similar to 9 degrees-14 degrees similar to 20 degrees. The amount of annual energy production predicted by the wind tunnel experiment model is about 51 % of the field experiment model. This study provides a better understanding of the wake characteristics and a guiding significance for the layout optimization of wind farms. (C) 2021 Elsevier Ltd. All rights reserved.