本文關(guān)鍵詞： 計(jì)算流體力學(xué) 行列式街區(qū) 錯(cuò)列式街區(qū) 流場(chǎng) 污染物濃度分布　出處：《華東師范大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著我國(guó)城市建筑布局日趨密集,機(jī)動(dòng)車保有量迅速增長(zhǎng),城市機(jī)動(dòng)車尾氣污染問題日益突出。為探討城市微尺度條件下不同街區(qū)風(fēng)場(chǎng)和污染物傳輸及分布特性,本文基于計(jì)算流體力學(xué)軟件FLUENT,采用RNG κ-ε湍流模型,首先使用數(shù)值實(shí)驗(yàn),與國(guó)外風(fēng)洞實(shí)驗(yàn)結(jié)果進(jìn)行比對(duì),驗(yàn)證了本文擬采用的數(shù)值方案合理性;在此基礎(chǔ)上,以典型城市街谷實(shí)況為原型,實(shí)現(xiàn)了非孤立三維行列式和錯(cuò)列式街區(qū)建模;以此作為研究對(duì)象,分別模擬研究了上述兩種城市街谷建筑布局內(nèi)部及其下風(fēng)向流場(chǎng),以及車輛直線穿越道路時(shí)的污染物濃度空間分布特征,并對(duì)流場(chǎng)和污染物濃度分布特征進(jìn)行了解釋。結(jié)果表明:無論是行列式還是錯(cuò)列式布局街區(qū),入流空氣由于受建筑群阻擋作用,均導(dǎo)致街區(qū)建筑群下風(fēng)方向產(chǎn)生低風(fēng)速渦旋區(qū),并聚集大量來自街區(qū)內(nèi)部的污染物。街區(qū)風(fēng)速入口附近,受狹管效應(yīng)作用,形成風(fēng)速最大值區(qū),相應(yīng)的污染物濃度最低;與以往研究結(jié)果一致,在高寬比為1的街道峽谷內(nèi)均產(chǎn)生了一個(gè)順時(shí)針渦旋,且污染物主要聚集在背風(fēng)面底層;污染物的擴(kuò)散與湍流強(qiáng)度及風(fēng)速密切關(guān)系,在高湍流區(qū)域和風(fēng)速較大的迎風(fēng)區(qū)表現(xiàn)為污染物濃度較低,反之,背風(fēng)區(qū)污染物濃度較高。對(duì)于錯(cuò)列式布局的街區(qū),街谷高寬比為1:3時(shí),出現(xiàn)尾干擾流,并在街谷內(nèi)出現(xiàn)多個(gè)渦流。據(jù)錯(cuò)列式布局街區(qū)目標(biāo)街谷統(tǒng)計(jì)結(jié)果可知,迎風(fēng)區(qū)、中心區(qū)及背風(fēng)區(qū)的風(fēng)速大小基本一致,錯(cuò)列式街區(qū)布局通風(fēng)效果更好;中心區(qū)湍流強(qiáng)度略大于迎風(fēng)區(qū),且均大于背風(fēng)區(qū);迎風(fēng)區(qū)污染物濃度最高,中心區(qū)次之,背風(fēng)區(qū)最小。通過對(duì)兩典型街區(qū)對(duì)比可知,錯(cuò)列式街區(qū)布局目標(biāo)街谷內(nèi)風(fēng)速、湍流強(qiáng)度和污染物濃度均更大。本文研究結(jié)果可以為合理設(shè)計(jì)街區(qū)布局、準(zhǔn)確預(yù)測(cè)污染物濃度分布和利用自然風(fēng)緩解城市高密度地區(qū)空氣污染提供科學(xué)依據(jù)。
[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.
【學(xué)位授予單位】：華東師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU119;X51

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