建筑结构龙卷风荷载试验中关键相似参数和缩尺比影响的研究

This project aims to investigating the effects of similarity parameters (kinetics similarity parameters, such as swirl ratio, aspect ratio, etc. and dynamics similarity parameters, such as Reynolds number, etc.) and scale ratios (geometric scale and velocity scale) in the tornado-induced wind loading experiment. The quantitative relationship between the geometric swirl ratio in simulated tornado vortices and real swirl ratio in full-scale tornado vortices would be studied, and the perennial problems of the accuracy in swirl ratio calculation in the physical simulation of tornado vortices would be solved. In addition, the quantitative evaluation methods of random wandering of the tornado vortex center would be proposed, and the quantitative relationship between parameters, like swirl ratio and aspect ratio, and wind field characteristics, such as three-dimensional velocity profile, pressure drop and random wandering of the vortex center, would be explicated. Furthermore, this project would study the variation of aerodynamic characteristics of cylinder and square cylinder with Reynolds number, and clarify the mechanism of Reynolds number effects and the variation of aerodynamic force. The effects of translation speed and geometric scale on tornado-induced wind loading acting on buildings would be determined by the contrast experiment using the tornado vortex simulators with different experimental capacities in Tongji University and Texas Tech University. This project intends to develop the new experimental criteria taking the swirl ratio and random wandering of vortex center as key kinetic similarity parameters. It will satisfy the imperious demands of developing new facilities and new methods in the process of making our country forward from big power in civil engineering to the great power in disaster prevention and mitigation, which possesses the theoretical value and application prospect for key projects.

本项目研究建筑结构龙卷风荷载试验中的相似参数（龙卷风涡流比、高宽比等运动学参数和雷诺数等动力学参数）和缩尺比（几何缩尺比和速度缩尺比）对风荷载试验结果的影响。研究龙卷风旋涡的几何涡流比和真实涡流比之间的定量对应关系，解决龙卷风模拟试验中长期存在的涡流比计算准确度问题；提出龙卷风涡核中心随机漂移的定量评估方法；明确龙卷风涡流比、高宽比和三维风速剖面、压力降以及涡核中心漂移之间的定量关系。研究龙卷风风场特性和圆柱、方柱的空气动力特性随雷诺数的变化，明确龙卷风作用下的雷诺数效应机理。利用具有不同试验能力的同济大学和德州理工大学风洞开展对比试验，明确移动速度和几何缩尺比对建筑龙卷风荷载的影响。本项目拟提出以涡流比和涡核中心漂移参数为关键运动学相似参数的新型试验准则。本项目满足我国从土木工程建设大国向防灾减灾强国迈进过程中研制新设备新方法的迫切需要，具有一定理论价值和重大工程应用前景。

具有共识的龙卷风风洞试验方法标准或指南是正确开展龙卷风荷载试验的保证，制定它的前提是阐明龙卷风荷载试验中的关键相似参数和几何/时间/速度缩尺比等试验参数对荷载试验结果的影响。至今为止，这方面的研究在国内外近于空白。本项目针对结构抗龙卷风设计的需要，具有一定理论价值和重大工程应用前景。. 本项目的主要研究内容和重要结果主要表现在以下三个方面：.1）龙卷风结构效应中的关键相似参数和缩尺比效应. 明确了龙卷风瞬态旋涡结构、最大切向速度和涡核半径、平均和脉动风速分布等流场特征随入流高宽比、涡流比、龙卷风移动速度、雷诺数等的变化规律；探明了龙卷风流场特征随多种涡流比定义的变化规律，提出了不同涡流比定义和真实涡流比之间的定量换算关系；.2）龙卷风旋涡漂移特性与机理. 研究了龙卷风旋涡中心的分布特征、旋涡漂移幅值沿龙卷风轴向的变化规律；研究了基于时间平均和涡核中心重定位修正的龙卷风三维速度分布；将瞬态龙卷风流场分解为平均成分、相干成分、过渡成分和噪声成分，结合能量分布特征阐明了龙卷风旋涡漂移的发生机理。.3）柱体结构龙卷风荷载的雷诺数效应. 针对柱体结构相对龙卷风涡核中心的不同径向位置，研究了柱体结构表面风压分布和其非高斯特性以及其雷诺数效应。将柱体结构龙卷风荷载分解为与气压降相关的风荷载和与气动效应相关的风荷载，并与常规大气边界层风作用下的风荷载进行了对比分析。明确了龙卷风作用的雷诺数效应机理。. 在执行课题的4年期间发表了标注本课题的期刊论文10篇，其中在本行业最高水准的国际学术杂志上发表英文SCI论文8篇，中文EI论文1篇。培养博士生1名。