城市街区不同建筑布局对风场和污染场的影响

发布时间：2018-02-10 19:53

本文关键词： 计算流体力学行列式街区错列式街区流场污染物浓度分布　出处：《华东师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着我国城市建筑布局日趋密集,机动车保有量迅速增长,城市机动车尾气污染问题日益突出。为探讨城市微尺度条件下不同街区风场和污染物传输及分布特性,本文基于计算流体力学软件FLUENT,采用RNG κ-ε湍流模型,首先使用数值实验,与国外风洞实验结果进行比对,验证了本文拟采用的数值方案合理性;在此基础上,以典型城市街谷实况为原型,实现了非孤立三维行列式和错列式街区建模;以此作为研究对象,分别模拟研究了上述两种城市街谷建筑布局内部及其下风向流场,以及车辆直线穿越道路时的污染物浓度空间分布特征,并对流场和污染物浓度分布特征进行了解释。结果表明:无论是行列式还是错列式布局街区,入流空气由于受建筑群阻挡作用,均导致街区建筑群下风方向产生低风速涡旋区,并聚集大量来自街区内部的污染物。街区风速入口附近,受狭管效应作用,形成风速最大值区,相应的污染物浓度最低;与以往研究结果一致,在高宽比为1的街道峡谷内均产生了一个顺时针涡旋,且污染物主要聚集在背风面底层;污染物的扩散与湍流强度及风速密切关系,在高湍流区域和风速较大的迎风区表现为污染物浓度较低,反之,背风区污染物浓度较高。对于错列式布局的街区,街谷高宽比为1:3时,出现尾干扰流,并在街谷内出现多个涡流。据错列式布局街区目标街谷统计结果可知,迎风区、中心区及背风区的风速大小基本一致,错列式街区布局通风效果更好;中心区湍流强度略大于迎风区,且均大于背风区;迎风区污染物浓度最高,中心区次之,背风区最小。通过对两典型街区对比可知,错列式街区布局目标街谷内风速、湍流强度和污染物浓度均更大。本文研究结果可以为合理设计街区布局、准确预测污染物浓度分布和利用自然风缓解城市高密度地区空气污染提供科学依据。
[Abstract]:With the increasing density of urban buildings and the rapid growth of vehicle ownership in China, the problem of vehicle exhaust pollution is becoming more and more serious. In order to study the transmission and distribution characteristics of wind field and pollutants in different urban blocks under the condition of urban micro-scale, Based on fluent, a RNG 魏-蔚 turbulence model is used in this paper. The numerical results are compared with those of foreign wind tunnel experiments, and the rationality of the proposed numerical scheme is verified. Taking the typical urban street valley as the prototype, the non-isolated three-dimensional determinant and staggered block modeling are realized, and the interior and downwind flow fields of the two urban street valley buildings are simulated and studied respectively. The spatial distribution characteristics of pollutant concentration and the characteristics of flow field and pollutant concentration distribution are also explained. The results show that: whether determinant or staggered layout block, The incoming air is blocked by the building group, which leads to the low wind speed vortex area in the downwind direction of the block building group, and accumulates a large number of pollutants coming from the block. Near the wind speed entrance of the block, it is subjected to the effect of narrow pipe. The corresponding pollutant concentration is the lowest in the maximum wind speed region, which is consistent with the previous research results. A clockwise vortex is produced in street canyons with a aspect ratio of 1, and the pollutants are mainly concentrated at the bottom of the leeward surface. The diffusion of pollutants is closely related to the turbulence intensity and wind speed. The pollutant concentration is lower in the high turbulence area and the upwind region with higher wind speed, whereas the pollutant concentration is higher in the leeward area. When the ratio of height to width of street is 1: 3, the tail interference flow appears and several eddy currents appear in the street valley. According to the statistical results of the target street valley in the staggered layout block, the wind speed in the upwind area, the central area and the leeward area is basically the same. The ventilation effect of staggered block layout is better; the turbulence intensity in the central area is slightly greater than that in the upwind area and is larger than that in the leeward area; the concentration of pollutants in the upwind area is the highest, followed by the central district, and the leeward area is the smallest. Staggered block layout the wind speed, turbulence intensity and pollutant concentration in the target street valley are higher. The results of this study can be used to reasonably design the block layout. Accurate prediction of pollutant concentration distribution and use of natural wind to mitigate air pollution in urban high density areas provide scientific basis.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU119;X51

【参考文献】