【作者】 江鹏；

【导师】 汪之松； 魏奇科；

【作者基本信息】 重庆大学 ， 工程硕士（建筑与土木工程领域）（专业学位）， 2018， 硕士

【摘要】 下击暴流是在雷暴天气中时常发生的一种极具破坏性的极端强风,是对近地面区域的建筑结构损害较大的短时局部强风。自研究学者从气象学角度定义下击暴流以来,国内外已有很多关于高耸结构、输电塔等遭受下击暴流的风致破坏的报道。随着结构风工程领域的不断完善,国内外学者对下击暴流展开了如现场监测、理论分析、风洞实验及数值模拟等研究手段对其风场及风荷载的一系列研究。以往对下击暴流风荷载的研究中,大多针对高层或高耸结构,对厂房等低矮型建筑研究较少;而且研究大多集中于静止型下击暴流,然而实测数据表明,风暴中心随着时间是移动的。针对上述问题,本文以单跨工业厂房为研究对象,基于风洞试验、大涡模拟方法、雷诺平均法分析方法,研究径向位置、风向角、移动效应等不同参数对下击暴流作用下厂房表面风压的影响。主要研究工作包括以下几个部分:（1）基于冲击射流测压试验及数值模拟研究径向距离对平屋面厂房表面风压的影响,研究在下击暴流风场中不同径向位置处厂房表面风压分布规律。分析表明:数值模拟与风洞试验结果对比具有较好的吻合性,变化趋势基本一致;在下击暴流作用下,径向距离对厂房表面风压影响较大,随着径向距离的增大,厂房表面平均风压系数有明显衰减趋势,脉动风压系数逐渐增大;在d=0.5D_jet径向位置处,厂房各表面均受正压,其余径向位置处,迎风面受正压,其余各表面受负压。（2）建立数值风洞,采用雷诺平均法（RANS）及大涡模拟方法（LES）,考虑不同风向角对厂房表面风压的影响,分析表明:0°与90°风向角,厂房周围流场较为对称,厂房表面风压系数分布较为均匀,而其余风向角,由于来流斜风的影响,各风向角下出现锥形涡旋,使得气流分布不对称,表面风压系数呈梯形分布;斜风使得表面风压突变,出现极值不利风压区域,且各风向角风压极值位置有所变化;风向角的变化,使得屋檐、屋脊、山墙及墙面转角等局部区域成为极值风压区域,在进行结构抗风设计时,设计风荷载应适当放大。（3）基于大涡模拟,在数值风洞中进行考虑移动效应的下击暴流作用下不同空间位置处厂房表面风压特性研究。分析表明:移动下击暴流作用下厂房表面风压出现动态的变化,在不同时刻及不同空间位置处,表面平均风压系数分布差异较大,厂房周围流场特性变化显著;当风暴中心位于厂房周围时,迎风面及屋面出现较大风压,在进行低矮建筑等围护结构设计时,应关注风暴中心移动对其表面风压的影响。更多还原

【Abstract】 Downburst is a very destructive extreme strong wind that often occurs during the thunderstorms.It is a short-term local strong wind that damages the building structure near the ground.Since the research scholars defined downbursts from a meteorological point of view,there have been many reports about on wind-induced damage caused by downbursts such as towering structures and transmission towers.With the continuous improvement of the structural wind engineering field,domestic and foreign scholars have conducted a series of researches on downburst storms such as site monitoring,theoretical analysis,wind tunnel experiments and numerical simulations on their wind fields and wind loads.Previous studies on downburst storm wind loads have mostly focused on high-rise buildings or high-rise structures.There have been few researches on low-rise buildings such as factories;moreover,most of the previous studies focused on static downburst storms.However,measured data indicate that storm centers have it is moving with time.In view of the above problems,this paper takes a single-span industrial plant as the research object,and based on the wind tunnel test,large eddy simulation method,and Reynolds average method analysis,under the action of the downburst,considering radial position,wind direction angle and moving effect parameters on the surface of the plant of the impact of wind pressure.The main research work includes the following sections:（1）Based on the impact jet pressure test and numerical simulation to study the influence of radial distance on the wind pressure on the surface of the flat roof factory,the distribution of wind pressure on the surface of the plant is studied under the action of the downburst.The analysis show that the comparison between numerical simulation and wind tunnel test results is in good agreement and the trend of change is basically the same;under the effect of downburst,the radial distance has a greater influence on the wind pressure on the surface of the building,and the radial distance increases.The average wind pressure coefficient of the plant surface has a significant attenuation trend,and the fluctuating wind pressure coefficient gradually increases.At the radial position of d=0.5D_jet,the surface of the factory building is under positive pressure.At the other radial positions,the windward surface is affected.Positive pressure,the rest of the surface under negative pressure.（2）Establish a numerical wind tunnel and use the Reynolds-Averaged Navier-Stokes method（RANS）and the large eddy simulation method（LES）to consider the influence of different wind direction angles on the wind pressure on the surface of the plant.The analysis show that the wind direction angles are 0°and 90°,and the flow field around the plant is relatively symmetrically,the distribution of wind pressure coefficients on the surface of the factory building is relatively uniform,while in the remaining wind direction angles,conical vortices appear at the wind angles due to the effect of inflow winds,making the distribution of air flow asymmetric,and the surface pressure coefficient is trapezoidal;The surface wind pressure was abruptly changed,and the extreme unfavorable wind pressure region appeared,and the wind-pressure extreme position of each wind direction changed;the change of wind-direction angle made the local area such as eaves,roof,gables and wall corner become extreme wind pressure.In this area,the design wind load should be appropriately enlarged when designing the wind-resistant structure.（3）Based on large eddy simulation,wind pressure characteristics of the plant surface at different spatial locations under the action of downbursts considering the movement effect are studied in numerical wind tunnels.The analysis show that the wind pressure on the surface of the plant under the action of moving downburst shows dynamic changes.At different moments and in different spatial locations,the distribution of the average surface pressure coefficient varies greatly,and the flow field characteristics around the factory building change significantly;when the storm center is located When the building is surrounded by large wind pressures on the windward side and the roof,when designing the low-rise building and other envelope structures,attention should be paid to the impact of the center of the storm on its surface wind pressure.更多还原