基于2013年马甸桥北气象塔实测数据的北京城区地貌风速谱分析

ANALYSIS OF THE WIND SPEED SPECTRUM IN THE URBAN AREA OF BEIJING BASED ON THE MEASURED DATA OF THE MA DIAN QIAO BEI METEOROLOGICAL TOWER IN 2013

基于实测的风场特性研究是结构抗风中的基础性工作之一。脉动风速谱作为风场特性的主要参数之一,描述了风的能量在频率上的分布情况。Van der Hoven最先测得的包括宏观气象尺度峰值和微观气象尺度峰值的风速谱在风工程领域具有奠基性贡献。由于早期采集设备精确性不高、计算分析水平不足,以及近年来城市化进程加快,城市地貌下全频率范围的风速谱有待进一步考查。该文采用2013年北京气象塔47 m、80 m和140 m高度处超声风速仪测得的风速数据,计算分析了反映宏观和微观气象尺度变化的全频率风速谱,并和Van der Hoven风速谱以及其他学者的实测谱进行了对比。结果表明:反映宏观气象尺度变化的低频风速谱除了在周期约为4天处存在峰值外,在周期约为1天(24小时)处的峰值非常明显,而在12小时周期处的峰值相对微弱;与宏观气象尺度峰值相比,高频微观气象尺度峰值较为微弱,且随高度增加,宏观气象尺度峰值逐渐增加,而微观气象尺度峰值相差不多。考虑到结构抗风设计时关注的是强风条件下的高频段风速谱,该文挑选平均风速大于8 m/s的风速样本,对其微观气象尺度风速谱进行了讨论,并和经典风速谱进行了对比,发现不同高度处的实测高频风速谱曲线相互吻合,且实测谱与Kaimal谱接近。

The study on full-scale wind field characteristics is one of the fundamental works in the structural wind-resistance design.Being one of the main parameters among them,the wind speed spectrum describes the distribution of turbulence energy with the frequency.Van der Hoven first proposed the wind speed spectrum in the wide frequency range,including the macro-meteorological and micro-meteorological peaks,which made a pioneering contribution in wind engineering.Considering that the data acquisition equipment and computing ability in early years were relatively poor and the urbanization is accelerating recently,the full-scale wind speed spectrum should be further examined in urban areas.The paper obtains the wind speed spectrum in a wide frequency range including the macro-meteorological and micro-meteorological peaks based on the wind speed data collected by the sonic anemometers at the heights of 47 m,80 m and 140 m of the Beijing Meteorological Tower in 2013.The wind speed spectrum is compared with the Van der Hoven spectrum and other previous spectra.The results show that for the macro-meteorological spectrum,besides around the 4-day cycle,the periodic deterministic component with a period of 24 hours is also detectable and prominent.However,the spectrum does not show significant peaks at a period of 12 hours.The micro-meteorological peak is relatively weak compared with the macro-meteorological peak.The macro-meteorological peak increases with the height,while the micro-meteorological peak shows little change for different heights.Considering that the wind spectrum in the high frequency range is the main focus of the structural wind-resistance design,the micro-meteorological spectrum is recalculated based on the strong wind speed samples whose mean wind speeds are larger than 8 m/s.The comparisons with typical power spectrum are performed.It is shown that the micro-meteorological spectrum for different heights generally correspond with each other,and they are shown to be close to the Kaimal spectrum.