针对街道峡谷内部气流场的参数化研究

Numerical relationship between street geometry,background wind and internal wind field in street canyon

为了建立一个能够快速且可靠地模拟街区尺度交通污染物三维分布的模型以应对实时在线模拟的需求,将城区的最小单位假定为两侧建筑物等高的长街区(街道峡谷),基于CFD模型对街道峡谷内部气流场的模拟结果,对街道峡谷内不同区域的气流(U、V、W 3个分量)与街区几何比例(高宽比HW和长宽比LW)、背景风(u和v 2个分量)的数值关系进行了回归分析。分析结果显示,分量U在非靠近边界的区域与街区几何比例和背景风线性相关性较好;分量V则在靠近地面或顶面的区域;分量W则是在靠近墙面的区域。利用回归分析得到的数值关系构建的参数化方法可以计算得到近似于CFD模型模拟结果的街道峡谷内部气流场。在此基础上,基于高斯模型建立了一个参数化模型,并以黑炭气溶胶BC为例对参数化模型进行评估,评估结果表明,参数化模型具有一定的实用价值。

The effects of street geometry（i.e.,the street width to building height ratio and street length to width ratio） and background wind（i.e.,velocity and direction） on the wind field distribution（i.e.,U,V,W）inside the street canyon are evaluated.Based on the multiple linear regression model,it is found that the parallel wind component U inside the street canyon is mainly driven by the background wind u component in most places except the places near the ground and building surfaces as well as top of the street canyon.Near these places,however,the penpedicular wind component V（near the ground and top of the street canyon） and vertical wind component W（near the building surfaces） response strongly to the background wind v component.The parameterized method in general agrees well with the CFD simulated results.By applying the Gaussian model,the parameterized wind field can be used to efficiently drive the dispersion of traffic-oriented pollution inside a typical street canyon.