青草背长江大桥桥位风速脉动特性实测分析

Field measurement analysis of wind turbulence characteristics at bridge site of Qingcaobei Yangtze River

为研究山区风场近地层风速的脉动特性,利用安装在青草背长江大桥上的高频风速仪对桥址处风场进行为期8个月的全程监控.根据实测风速序列分析了在桥址处平均风速、风向、湍流强度、阵风因子和功率谱的统计特征,并针对山区风阵风因子随湍流强度变化关系以及不同计算时距条件下阵风因子的换算关系进行了探讨.研究结果表明：受局部热力环流的影响,桥址风场具有明显周期性变化特征;高风速下顺风向湍流强度及竖向风速相对湍流强度大于桥梁抗风设计规范建议值,而横风向相对脉动强度则比桥梁抗风规范值小;阵风因子随阵风计算时距的变换规律可以用对数高斯函数加以描述;山区复杂地形、地貌导致风速中湍流成分发育更为充分,湍流高频能量相对较大,脉动风速谱在高频段比规范推荐风谱大,低频段比规范推荐谱小.

To obtain the wind turbulence characteristics in mountainous area,wind field at Qingcaobei Bridge site was monitored by high-frequency anemometer during eight months.The wind speed,wind direction,turbulence intensity,gust factor and power spectra were analyzed based on these field measured data.Subsequently,the variation of gust factor with turbulence intensity and the relationship between gust factor and time interval in mountainous areas were investigated.Research results show that the mean wind speed and its direction in mountainous area show obvious periodic variation characteristics,which may be reduced by the local thermal circulation.The turbulence intensity of longitudinal and vertical fluctuation components in mountainous area is higher than the recommended value at high wind speed,but the horizontal direction is opposite.The variation of gust factor with the time interval in mountain area can be described by the logarithmic Gauss function.The turbulence energies at high frequencies are higher than the recommended value while lower at low frequencies,which is contributed by the fully developed turbulence caused by great topographic relief in mountain area.