运动龙卷风冲击高层建筑数值模似

发布时间：2018-01-25 13:26

本文关键词： 龙卷风高层建筑风荷载冲击效应数值模拟　出处：《中国科学技术大学》2015年硕士论文　论文类型：学位论文

【摘要】：龙卷风具有较强的破坏力,是抗风减灾工程重要的防范对象之一。近年来,随着地球环境的恶化,龙卷风袭击大型城市的灾害时有发生,针对城市中高层建筑的龙卷风灾害研究开始受到重视。已有的研究多集中于实验尺度模型和准静态荷载,而对龙卷风动态冲击全尺寸高层的研究还比较少,特别是现行建筑设计规范仍没有针对龙卷风给出结构设计及安全方面的具体要求和方法,迫切需要从理论模拟及实验等多方面开展研究。本文首先建立了动态运动龙卷风的数值风场模型,应用大涡模拟(LES)方法开展了龙卷风动态冲击高层建筑的非定常过程模拟,对其漩涡演化及对高层建筑的冲击风荷载特性开展了初步研究,并与实验室尺度下的荷载特征进行了比较研究,进一步搞清了龙卷风冲击不同尺度和形状的高层建筑流场差异和荷载产生机理,主要获得如下结论：1)在模拟龙卷风动态运动的数值风场模型中,简单采用动态速度边界条件较难保持龙卷风在运动过程中的形态和强度不变,采用预设旋转强度和速度保持恒定的数值驱动区是一种较简便且高效的计算方法。2)实验室尺度下的数值模拟结果表明：龙卷风动态冲击高层建筑,其荷载响应特性与建筑尺度有关。建筑尺度较小时,冲击荷载呈双峰特征,冲击效应和时变效应相对较小。相反,冲击荷载呈多峰特征,时变性强,冲击效应明显。同时,龙卷风在冲击较大尺度建筑时,主涡会发生破裂,形成多个漩涡。多漩涡之间以及与建筑尾涡相互作用和耦合将导致更大的冲击荷载。这种力学现象在国内外龙卷风研究中尚未发现类似报道。3)全尺寸龙卷风冲击高层建筑的载荷响应特性与实验室模拟尺度下的载荷响应特性存在相似特性与尺度效应。其相似性体现在：当龙卷风尺度与建筑尺度比相似时,其荷载变化规律和特征存在一定相似性。不过其具体载荷系数及峰值响应位置却存在较大差异,这反应了龙卷风的尺度效应。4)全尺寸模拟结果表明：当建筑模型的高度相同,尺度相近时,建筑的外形跟载荷响应的大小有一定的关系。综合不同建筑的龙卷风载荷载荷响应特性上看,矩形建筑的龙卷风载荷响应系数相对较大,且与龙卷风袭击攻角有关。
[Abstract]:Tornadoes have strong destructive power, which is one of the important protection objects of wind disaster mitigation engineering. In recent years, with the deterioration of the earth environment, tornadoes frequently hit large cities. The research on tornado disasters of high-rise buildings in cities has been paid more attention. Most of the existing researches focus on the experimental scale model and quasi-static load, but the research on tornado dynamic impact on the full scale high-rise is relatively rare. In particular, the current building design code still does not give the specific requirements and methods of structural design and safety for tornadoes. There is an urgent need for theoretical simulation and experimental research. Firstly, the numerical wind field model of dynamic moving tornadoes is established in this paper. The unsteady process of tornado dynamic impact on high-rise buildings is simulated by means of large eddy simulation (les) method. The vortex evolution and impact wind load characteristics of high-rise buildings are studied preliminarily. Compared with the load characteristics of laboratory scale, the flow field difference and load generation mechanism of high-rise building with different scale and shape of tornado impact are further understood. The main conclusions are as follows: 1) in the numerical wind field model of simulating tornado dynamic motion, it is difficult to maintain the shape and intensity of tornado in the course of motion by simply adopting dynamic velocity boundary condition. Numerical driving region with preset rotation strength and constant velocity is a simple and efficient calculation method. 2) numerical simulation results at laboratory scale show that tornadoes impact on high-rise buildings dynamically. The load response characteristics are related to the building scale. When the building scale is small, the impact load is bimodal, while the impact effect and time-varying effect are relatively small. On the contrary, the impact load is multi-peak and time-varying. The impact effect is obvious. At the same time, when tornadoes impact large scale buildings, the main vortex will break down. The formation of multiple whirlpools. The interaction and coupling between multiple whirlpools and building trailing vortices will lead to larger impact loads. This mechanical phenomenon has not been reported in tornadoes at home and abroad. The load response characteristics of full-scale tornado impact high-rise buildings are similar to those of laboratory simulation scale. When the scale of a tornado is similar to that of a building. The law and characteristics of load variation are similar, but the load coefficient and peak response location are different. This reflects the scale effect of tornadoes. 4) the full-scale simulation results show that when the height of the building model is the same and the scale is similar. The shape of the building has a certain relationship with the size of the load response. Considering the tornado load response characteristics of different buildings, the tornado load response coefficient of rectangular buildings is relatively large. And with tornadoes attack angle of attack related.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU973.213

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