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

为了实现城市建筑物和构筑物的防风减灾，正确评估100~200m海拔地区的风特性是非常重要的。然而，地面被各种物体覆盖，建筑物形状复杂，植被种类繁多，靠近地面的空间并不均匀。特别是在城市地区，中高层建筑密集建造，因此在几十米到一百米的高度范围内，空间方面的差异很大。本研究基于近年来CFD(计算流体动力学)技术的迅速发展，利用本项目人员开发的计算程序，建立了直接反映城市地面各建筑物实际形状的数值模型，能够较高精度地预报大风的湍流结构。通过大涡模拟(LES)，研究了大风阵风的结构及其受地表粗糙度条件及其形状或起伏的影响。利用所获得的结果和信息，实现了建筑物和构筑物在大风作用下的结构安全，并进行了抗风设计的精细化。

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.