低矮房屋风荷载实测研究(Ⅰ)——登陆台风近地边界层风特性

Field measurements of wind loads on a low-rise building——PartⅠ: Near-surface boundary layer wind characteristics of landfall typhoons

基于可移动双坡屋面实验房及测风塔获取的"苏迪罗"、"彩虹"、"凯萨娜"和"芭玛"等台风登陆期间的三维脉动风速数据,对近地边界层平均风特性和湍流特性进行分析。分析结果表明:近地100m范围内平均风速剖面符合对数律和指数律分布,平均湍流度剖面符合指数律分布;与良态季风条件下相比,摩擦速度、地面粗糙度长度、平均风速剖面指数α值相对变大,平均湍流度相对增大20%以上;湍流度与阵风因子相关性与Ishizaki实测结果一致;纵向、横向和竖向三湍流分量的竖向相干函数衰减指数为16.82、7.23、3.69;离地3.2m高度处各向湍流分量的功率谱值大于10m高度功率谱值2倍以上,在低频范围各向湍流分量含能量相对要大,湍流功率谱高频段下降相对较快,在惯性子区各湍流分量的功率谱的分布显著偏离"Kolmogrove-5/3"律。

This paper investigates the mean wind speed and wind turbulence characteristics of typhoons in boundary surface layer based on monitored three-dimensional high resolution wind data during landfall of typhoons ＂Soudelor＂, ＂mujigae＂, ＂ketsana＂ and ＂parma＂. The analysis results revealed that in the near-surface range （ 〈 100m） vertical distribution of mean wind speed on seashore can be well described by a logarithmic law and power law. The variation of the mean longitudinal turbulence intensity with height approximately follows a power law. Comparing with those obtained under monsoon wind climates, there are apparent increases in shear stress velocity, surface roughness length and the exponent of power-law profile. The average values of turbulence intensity observed during the typhoons are more than 20% higher than those obtained during the monsoons. The relation between turbulence intensity and gust factor is proposed, which is in favorable agreement with that obtained by Ishizaki. The mean decay coefficients in the root coherence functions of the longitudinal, lateral and vertical wind components are 16.82, 7.23 and 3.69, respectively. Estimates of the normalized power spectra at 3.2m height are two times larger than those at 10m height for the three wind components. The observed normalized power spectra of longitudinal, lateral and vertical wind components during the typhoons have significant more energy at lower frequencies and fall faster at high frequencies than the spectra descried by Kolmogrove theory for non-typhoon winds. The slope rates of turbulence spectra of the longitudinal, lateral and vertical wind components do not satisfy the-5/3 law in the inertial range.