Characteristics of wind turbulence near the boundary layer in Three-North Regions of China

Abstract

Based on the daily 10-minute wind observation data of the wind tower in CWERPON from 2013 to 2017, this study analysed the distribution and variation characteristics of wind turbulence in different gradients and periods in wind resource rich regions in NEC, NC and NWC. Results showed that: 1) The average wind speed from ground to 100 m height was 6.7m/s, which increased with the height, and the dominant wind speed was 4.0 m/s. The average wind speed at the height of 10 m, 30 m, 50 m, 70 m and 100 m were 6.0 m/s, 6.4 m/s, 6.7 m/s, 7.0 m/s and 7.5 m/s respectively. The highest and the lowest wind speed frequency occurred at the heights of 10m and 100m layers, which accounted for more than 22.5 % and 12.5 %. Starting from the wind speed of 6.0 m/s, the proportion of lower layers wind speed decreased, while that of high layers wind speed increased. 2) The average It decreased from low layers to high layers. Each layer’s It decreased gradually with the increasing of wind speed. The It values were different among these three regions in the study area, the NEC region was the largest, followed by the NWC, and the It value in NC stations were the smallest. Under the wind speed of 3.0-25 m/s and 15.0 m/s, the average It of each layer were 0.118 and 0.099 respectively; the maximum values were 0.189 and 0.120 at the height of 10 m in NEC region, and the minimum were 0.082 and 0.063, both of which appeared in the 100 m gradient in NC region and NWC region respectively. 3) The variation ranges of It among adjacent layers were different, the lower the layer was, the greater range of change occurred. The differences between the 10-30 m, 30-50 m, 50-70 m were 0.028, 0.013 and 0.003 respectively. 4) Each layer’s It corresponded to the variation trend of the air temperature. It increased slowly from 06:00, which reached the maximum value around 14:00, and then decreased slowly. 5) The wind turbine reach the C and B turbulence intensity level respectively at the height of 30 m and 10 m in the study area when the average wind speed is lower than 6.0 m/s, and some stations’ wind turbine type in these three regions should be at least A level.