LES Model for Wind Gusts over Urban Areas Represented by Buildings and Vegetations and Its Application to the Sophisticated Wind-Resistant Design

正确评价100 ~ 200 m高度区域的风特性，对于实现城市建筑物的风灾减灾具有重要意义。然而，地面上覆盖着各种各样的物体，如形状复杂的建筑物和多种植被，并且接近地面的空间是不均匀的。特别是在城市地区，中高层建筑密集，因此在几十米到一百米的海拔范围内，空间方面变化很大。在本研究中，基于近年来快速发展的CFD（计算流体动力学）技术，我们利用本项目人员开发的计算代码来构建数值模型，该模型直接由城市地面上的每个建筑物的实际形状来表示，并且可以高精度地预测强风的湍流结构。本文采用大涡模拟（LES）方法，研究了地面粗糙度、地形起伏对阵风结构及其脉动特性的影响。同时，利用所获得的结果和信息，实现了建筑物和构筑物的结构安全性，并进行了抗风设计的复杂性。

In order to realize the wind hazard mitigation for buildings and structures in urban area, it is important to evaluate correctly the wind characteristics in the altitude region at 100 to 200 m. However the ground surface is covered by various objects such as buildings with complicated shape and many sorts of vegetations, and the space close to the ground is not uniform. Especially, in urban area middle- and high- rise buildings are densely built, so that spatial aspect varies very much in the altitude range of tens meters to a hundred meters. In this research, based on the recent rapid development of CFD (Computational Fluid Dynamics) technique, we utilize the computational code developed by the staff of this project for constructing the numerical model which is directly represented by the actual shape of each building on the ground surface in urban area and can predict the turbulence structures of strong wind with high accuracy. The large eddy simulation (LES) is carried out, in order to clarify the structures of strong wind gust and its fluctuation characteristics influenced by the roughness conditions of ground surface and its shape or undulation. Also, utilizing the results and the information obtained, the structural safety of buildings and structures against strong wind is realized and the sophistication of the wind-resistant design is performed.