1.Dalian University of Technology;2.Chongqing University
National Key Research and Development Program of China (No. 2016YFC0701103)
At present, most of the studies on the wind field characteristics of downburst mainly focus on the wind speed model and a few characteristics. Few studies on the relationship between wind field characteristics and mean wind speed, the correlation between different wind field characteristics or the comparison with the boundary layer surface wind characteristics are carried out. Based on the measured wind speed data of downburst, the time-varying mean wind speed of downburst is extracted by utilizing the moving average method, and then the fluctuating wind speed is obtained. On this basis, the characteristics of turbulence intensity, turbulence integral scale and gust factor of downburst are further studied. The relationships between the above 3 characteristics and mean wind speed, as well as the correlations among the above 3 characteristics are analyzed. The results show that: (1) the turbulence intensity, turbulence integral scale and gust factor of downburst are greater than the corresponding wind field characteristic of atmospheric boundary layer surface wind at the same height under the corresponding site category; (2) there are negative correlations between turbulence intensity and mean wind speed, as well as between turbulence integral scale and turbulence intensity, while positive correlations exist between turbulence integral scale and mean wind speed, as well as between gust factor and turbulence intensity; (3) the wind resistance design for low-rise buildings should focus on the influence of fluctuating components of downburst, while the threat of airflow vortexes of downburst should be paid more attention for high-rise buildings and high-rise structures; (4) compared with the atmospheric boundary layer surface wind, downburst is prone to produce larger instantaneous extreme wind speed, which could pose greater threats to engineering structures.