摘要
为了对城市边界层的特殊风场特性进行研究,利用位于北京中心城区325 m气象观测塔,在9个不同高度布置超声风速仪,得到了2013—2017年间风速、温度连续观测的实测数据。统计分析表明:北京城区以良态风为主,盛行北风、西北风及南风,但强风主要来自西北向;除昼夜温度变化外,城市边界层的热量交换很大程度受到下垫面逆辐射影响。城市边界层大气的流动机制与平坦开阔地貌不同,且具有明显的分层结构;强风中,粗糙子层内中性层结占比达到97%;惯性子层以不稳定层结为主,混合层则以稳定层结为主,中性层结所占比例分别为40%、25%。对筛选出的强风样本分析表明,受到城市边界层分层结构的影响,100 m以下及以上平均风速剖面的变化规律略有不同,整体上,指数律模型较为适用,但现行规范对地貌参数的规定偏于保守;纵向湍流强度在粗糙子层(47 m)和惯性子层(140 m)均波动较大,在混合层(280 m)波动较小,不同子层测得的脉动风速谱均与von Karman谱相吻合;混合层中,涡旋横向和竖向尺度占比明显大于惯性子层及粗糙子层。
In order to study the special wind field characteristics of the urban boundary layer,nine ultrasonic anemometers were arranged at different heights of the 325 m meteorological observation tower located in the central urban area of Beijing,and the measured data of wind speeds and temperature from 2013 to 2017 have been recorded continuously.The statistical analyses show that it presents the normal wind climate in Beijing prevailing the north,northwest and south winds,of which the strongest winds are mainly from northwest.In addition to the diurnal temperature variations,the heat exchange in the urban boundary layer(UBL)is greatly affected by the back radiation of the underlying surface.The air flow mechanism of the UBL is different from that from the flat and open landform,which appears an obvious atmospheric stratification.Considering the strong wind records,the neutral stratification in the roughness sub-layer(RSL)accounts for 97%.The inertial sub-layer(ISL)is dominated by the unstable stratification,the mixed layer(ML)is dominated by the stable stratification,and the proportions of the neutral stratification are 40%and 25%,respectively.The analyses of the strong wind samples selected show that the mean wind speed profiles below and above 100 m are slightly different due to the stratification structure of the UBL.Overall,the wind speed profiles conform to the exponential model,while the geomorphic parameters recommended in the code appear to be more conservative.The longitudinal turbulence intensity fluctuates greatly in the RSL(47 m)and the ISL(140 m),but less in the ML(280 m),and the power spectral densities of fluctuating wind speeds in different sublayers are consistent with the von Karman spectrum.The proportion of the horizontal and vertical scales of the vortex in the ML is significantly larger than that in the RSL and ISL.
作者
张鑫鑫
李波
张石
杨庆山
田玉基
ZHANG Xinxin;LI Bo;ZHANG Shi;YANG Qingshan;TIAN Yuji(School of Civil Engineering,Beijing Jiaotong University,Beijing 100044,China;Beijing’s Key Laboratory of Structural Wind Engineering and Urban Wind Environment,Beijing Jiaotong University,Beijing 100044,China;School of Civil and Transportation Engineering,Beijing University of Civil Engineering and Architecture,Beijing 100044,China;School of Civil Engineering,Chongqing University,Chongqing 400044,China)
出处
《建筑结构学报》
EI
CAS
CSCD
北大核心
2022年第3期109-117,共9页
Journal of Building Structures
基金
国家自然科学基金项目(51878041)
高等学校学科创新引智计划资助项目(B13002)。
关键词
城市边界层
风场特性
实测
分层结构
平均风
脉动风
urban boundary layer
wind field characteristic
field measurement
stratification structure
mean wind
fluctuating wind
