地面粗糙度对结构龙卷风荷载影响的研究

发布时间：2018-01-20 14:16

本文关键词： 龙卷风 CFD数值模拟漩涡比离散相模型地面粗糙度平移龙卷风　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：龙卷风是一种超强的旋风,具有极大的破坏力。鉴于龙卷风发生的概率非常小,现今国内《建筑结构荷载规范》中还没有列出结构抗龙卷风设计的相关条款。然而,在设计核电厂等一些极其重要设施时,则必须明确考虑结构遭遇龙卷风的因素。地面粗糙度不仅是气象学中常用的一个重要参数,同时也是决定龙卷风风场结构的一个重要参数。因此本文所研究的地面粗糙度对龙卷风风场特性及建筑表面荷载的影响可为后续研究龙卷风提供一定的有用信息,也可为核电厂等极其重要的结构抗龙卷风设计及选址提供一定的参考。本文主要研究内容如下：1、基于CFD数值模拟方法,对不同漩涡比作用下的龙卷风风场特性进行了研究。为研究多漩涡龙卷风场结构的特征,利用大型流体软件FLUENT14.5的SSTk-ω湍流模型模拟了三种典型漩涡比值为0.28、0.5及1.0的龙卷风场,通过离散相模拟技术得到了准静态龙卷风的结构形态图。分析了不同漩涡比作用下龙卷风切向速度曲线变化图及速度矢量图的分布特征。并对不同漩涡比龙卷风场中的建筑物表面风压系数进行了模拟。结果表明,多漩涡龙卷风作用下的结构表面风压系数绝对值更小。2、同样基于CFD数值模拟方法,研究了B类地形下的地面粗糙度(y0为0、0.1及0.25)对龙卷风近地风场产生的波动而对建筑物表面荷载所造成的影响。根据上文结果选取了漩涡比值为0.5,并把均匀砂粒模型作为等效地面粗糙度,较详细地分析了地面粗糙度作用下龙卷风风场结构特征及建筑物表面风压系数的分布情况。结果表明,地面粗糙度起到了减小龙卷风核心半径以内的切向速度及增强龙卷风核心半径外的切向速度的作用,并造成龙卷风的核心半径变大；随着粗糙度的增大建筑物表面风压系数的绝对值也随之变大。3、为更加真实研究龙卷风对结构荷载的影响,研究了地面粗糙度对平移龙卷风结构荷载的影响。利用CFD数值模拟研究了平移龙卷风与静态龙卷风场特征的区别,其中平移龙卷风核心半径处的最大切向速度明显大于静态龙卷风；并分析了在地面粗糙度作用下的平移龙卷风结构表面风压系数的变化规律。结果表明,建筑物表面分布的风压系数都为负值,即表示龙卷风中心在建筑表面产生了风吸力；粗糙度长度越大的情况下,在建筑物靠近左侧一方的位置处的风压系数绝对值越大,其它位置处的绝对值只是局部增大；而左右两侧中心位置处的风压系数的绝对值随着粗糙度长度变大而变大。
[Abstract]:Tornadoes are super cyclones with great destructive power, given the very small probability of tornadoes occurring. At present, there are no relevant provisions on the tornado resistant design of structures in China. However, in the design of nuclear power plants and other extremely important facilities. The ground roughness is not only an important parameter in meteorology. It is also an important parameter to determine the structure of tornado wind field. Therefore, the influence of ground roughness on tornado wind field characteristics and building surface load can provide some useful information for further research on tornado. . It can also provide some reference for the design and site selection of the most important structures, such as nuclear power plant. The main contents of this paper are as follows: 1, based on CFD numerical simulation method. The characteristics of tornado wind field under different swirl ratios are studied. Using the SSTk- 蠅 turbulence model of the large-scale fluid software FLUENT14.5, the tornado fields with the ratios of 0.28g 0.5 and 1.0 are simulated. By means of discrete phase simulation technique, the structure shape diagram of quasi static tornado is obtained, and the distribution characteristics of tornado tangential velocity curve and velocity vector chart under the action of different swirl ratio are analyzed, and the tornadoes with different swirl ratios are analyzed. The wind pressure coefficient of the building surface in the field is simulated. The absolute value of the wind pressure coefficient of the structure surface under the action of multi-whirlpool tornado is smaller than that of the others. Based on the CFD numerical simulation method, the surface roughness of B type terrain is studied to be 0. The influence of 0.1 and 0.25) on the surface load of the building due to the fluctuation of the wind field near the ground. According to the above results, the swirl ratio is 0.5. Taking the uniform sand model as the equivalent surface roughness, the structure characteristics of tornado wind field and the distribution of wind pressure coefficient on the building surface under the action of ground roughness are analyzed in detail. The roughness of the ground reduces the tangential velocity within the core radius of the tornado and strengthens the tangential velocity outside the core radius of the tornado, and results in the increase of the core radius of the tornado. With the increase of roughness, the absolute value of wind pressure coefficient on the building surface also becomes larger. 3, in order to study the effect of tornado on the structure load more truly. The influence of ground roughness on the structural load of translational tornadoes is studied. The difference between the characteristics of translational tornadoes and static tornadoes is studied by CFD numerical simulation. The maximum tangential velocity of the translational tornado core radius is obviously larger than that of the static tornado. The variation law of wind pressure coefficient on the surface of the translational tornado structure under the action of surface roughness is analyzed. The results show that the wind pressure coefficients of the surface distribution of buildings are all negative. That is to say, the center of the tornado produces wind suction on the surface of the building; The bigger the roughness length is, the greater the absolute value of wind pressure coefficient is at the position near the left side of the building, while the absolute value at the other position is only local increase. The absolute value of the wind pressure coefficient at the center of the left and right sides increases with the length of roughness.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU312.1

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