【作者】 王轩；

【导师】 汪之松；

【作者基本信息】 重庆大学 ， 土木工程， 2014， 硕士

【摘要】 下击暴流是一种常见的强对流天气现象，有时对于人类正常活动会造成一定影响，甚或带来一些灾难。之前对下击暴流的的研究主要应用于气象航空等领域，针对建筑物的下击暴流风场风荷载的研究不多。荷载规范中的风荷载只考虑了一般情况的大气边界层风，针对极端天气如下击暴流风并未涉及。本文采用CFD数值模拟的方法考察下击暴流的风场规律并引入地形因素，考察山地地形的下击暴流风场特点，为之后的下击暴流风荷载研究以及即将进行的风洞试验奠定一定基础。(1)通过采用多种湍流模型进行数值模拟对比分析表明RNG k-ε模型与现有实测和理论数据吻合较好，因此本文选定RNG k-ε的湍流模型，并以1:1000的比例尺建立几何模型进行风场的数值模拟。平地下击暴流风场模拟结果表明不同径向位置风剖面有明显差异，但是无量纲后与理论模型和实测结果吻合较好。下击暴流下吹速度对于下击暴流风场的影响很小；风暴中心直径对于风场的影响仅局限于风场域的大小，而对无量纲风剖面曲线基本没有影响。下吹距离与风暴中心直径的比值(H/D值)对具体的风剖面影响较大，但是无量纲化后的风剖面基本一致，说明不同的H/D值产生的风场仍然保持了下击暴流的基本特性。(2)按照荷载规范的山坡地形，引入到下击暴流风场中，发现在坡顶有明显的加速效应。在坡顶后0.075D的距离再考察平地和坡地的下击暴流风剖面时，发现已经基本重合，即坡地对于风场的影响已经可以忽略。坡地的坡度大小对于风场的影响还是比较明显的，坡度越大，近地区域即风场高度Z<0.04m的区域加速效应越明显。坡顶位置的变化对于风场也有一定的影响。下击暴流的下吹速度对于下击暴流风场几乎没有影响，下击暴流H/D值对加速区域大小有影响，而对风场的实质影响有限。(3)余弦形山体地形山顶处的加速效应较坡地地形稍小一些，但对风场的影响范围较坡地地形大很多。下击暴流的下吹风速对山地地形的风场基本没有影响；下击暴流的H/D值对风场的影响同坡地相似，只对风场域和风剖面有影响而对加速因子曲线影响不大。改变山体坡度所得结果与坡地结果对比说明坡度相同时地形的改变并没有改变风场的特性。山体位置对加速因子曲线的影响趋势相同，只是大小有差异，峰值加速因子是随坡顶位置到风暴中心的距离的增大而增大。更多还原

【Abstract】 Downburst is a common phenomenon of strong convective weather, sometimes forhuman activities will cause some impact, even bring some disaster. Priorresearch to thedownburst mainly applied in meteorology and aviation field. There is little researchcontraposed the building on the downburst winds and downburst wind loads. Theloadcodein China did not involve the extreme weather such as downburst.This paperattempts to adopt numerical simulation CFD methods to investigate the law ofdownburst winds, consider the influence of topography, study the characteristics ofdownburst winds in mountainous topography and laythe foundation for wind tunnel test.Through the analysis, this thesisdrawsthe following conclusions:（1）Firstly, by using a variety of turbulence models to simulate, select the RNGk-εturbulence model which was consistent with the existing measured and theoreticaldata to do the following research work. The simulation results shows that at differentradial positions the wind profile is different, but the normalized results correspond to thetheoretical and experimental models. The outflow speed of downburst has little effect onwinds；The impact of the downburstcenterdiametertothe winds is limited to the size ofthewind field, and the downburstcenterdiameter has no influence to the wind profile.Theratio—height of downburst/downburstcenterdiameter（H/D）make a strong impact onthe wind profile, but normalized wind profile was consistent.It illustrates that thedifferent downburstcenterdiameter maintain the basic characteristic of downburst.（2）According to loadcode8.2.2, the escarpment topography is be considered indownburst winds. In the top of the escarpment there is a significant acceleration effect.At the the0.075D distance after the top of the escarpment, the wind profile has beenfound to substantially coincide with the flat wind profile, thereby the impact of thetopography has almost disappeared. The size of slope impacts the winds obviously, thegreater the slope, near-Earth region that Z <0.04m forregional acceleration effect ismore obvious. Changes in the position of a hill there is a certain influence on thedownburst winds. The blowing speed of downburst barely influence the downburstwinds, the H/D value influence the acceleration region size, and has no impact on thewinds.（3）The accelerating on the top of cosine-shaped mountain is smaller than theescarpment,but for the effect of topographyin wind,the cosine-shaped mountain is more obvious than the escarpment.The velocity in the center of downburst has no impact onthe downburst wind.The effect of H/D values in downburst is similar to the escarpment,The results obtained with the different slope of the cosine-shaped shows that thedifferent of terrain does not change the characteristics of the wind farm. Changing theposition of the mountain and found the same acceleration curve trend factor, butdifferent sizes, with the crest of the peak acceleration factor is the position of thedistance to the center of the storm increases.更多还原