本文選題：建筑參差比　切入點：重密度氣態(tài)污染物　出處：《湖南工業(yè)大學》2017年碩士論文

【摘要】：隨著計算機和數值模擬技術的飛速發(fā)展和廣泛應用,利用計算流體動力學方法研究城市街區(qū)中的污染物擴散問題已經成為一種高效、便利的研究手段。在城市街區(qū)的污染問題中,污染物自身的特性是決定其在街區(qū)峽谷中的擴散方式的重要因素。重密度氣態(tài)污染物不同于能夠輕易被城市風攜帶進而被稀釋的密度近或輕于空氣的氣態(tài)污染物,其因受限于本身密度大、重量大的特性,缺乏良好的跟隨性,因此,重密度氣態(tài)污染物在城市街區(qū)中的擴散方式有一定的研究意義。本文主要利用計算流體動力學方法,分別選用參差比為0.0,0.2,0.4,0.6和0.8等5種建筑模型,探討了分別位于城區(qū)外的重密度污染源和位于城區(qū)中心的重密度氣態(tài)污染源,在水平自然風條件下于不同參差比建筑物間的沉積過程,以及探究街區(qū)內行人區(qū)重密度氣態(tài)污染物的分布與建筑參差比之間的關系。本文首先通過對位于城市街區(qū)外的汞源受郊外來風影響在城市街區(qū)中擴散的穩(wěn)態(tài)情況進行模擬,研究城市街區(qū)建筑物高低錯落分布的布局對汞蒸氣在城區(qū)中擴散的影響。模擬結果發(fā)現,城市街區(qū)不同高度建筑物錯落分布會促進高空汞污染源在行人區(qū)的聚集,使得街區(qū)行人區(qū)汞濃度明顯增大;并且隨著街區(qū)建筑物參差比的增大,最高汞濃度值所在的街道逐漸向汞源方向靠近,較高建筑物背風面街道行人區(qū)汞質量流量明顯高于較矮建筑物背風面街道行人區(qū)汞質量流量。然后結合時間線對街區(qū)中心爆發(fā)的甲苯在城市風作用下于街區(qū)中的擴散情況進行非穩(wěn)態(tài)模擬,探究甲苯的擴散與時間與城區(qū)建筑參差比的關系。結果發(fā)現,當街區(qū)建筑高度一致時,甲苯擴散到下風向街道所花費的時間比建筑高度不一致時短;當街區(qū)建筑高度不一致時,位于較高建筑背風面街道的甲苯濃度普遍高于位于較矮建筑背風面街道的濃度;當建筑高度一致時,各街道的甲苯濃度隨時間延長而降低,但當建筑高度不一致時,位于下風向街道的甲苯甚至會重新聚集回到行人區(qū);經過一段時間后,爆發(fā)源所在街道的甲苯濃度屬建筑參差比為0.4的街區(qū)甲苯濃度最高,其次為建筑參差比為0.6和0.8的街區(qū),最后為建筑參差比為0.2和0的街區(qū)。最后還利用PIV粒子圖像測速系統(tǒng)測量了縮比例尺的城市街區(qū)水箱模型內的流場,驗證了計算流體動力學(computational fluid dynamics,CFD)在研究城市街區(qū)氣流組織問題上的準確性。本文結合穩(wěn)態(tài)和非穩(wěn)態(tài)的數值模擬,探究了重密度氣態(tài)污染物在建筑物高低不同錯落分布的城市街區(qū)中的擴散規(guī)律。研究結果城市街區(qū)人居環(huán)境中的針對重密度氣態(tài)污染物的治理工作提供了理論依據,有利于城區(qū)中受污染街道的具體位置和不同街道受污染的程度等級的確定,具有一定的實際意義。
[Abstract]:With the rapid development and wide application of computer and numerical simulation technology, the use of computational fluid dynamics (CFD) to study pollutant diffusion in urban blocks has become an efficient and convenient means of research.In the problem of urban district pollution, the characteristic of pollutant itself is an important factor to determine its diffusion mode in the district canyon.Heavy density gaseous pollutants are different from gaseous pollutants which can be easily carried and diluted by urban wind. Because they are limited by their own characteristics of high density and heavy weight, they lack good follow-ability.The diffusion of heavy density gaseous pollutants in urban blocks is of great significance.In this paper, using computational fluid dynamics (CFD) method, five kinds of building models, such as 0. 0. 2 0. 2, 0. 4, 0. 6 and 0. 8, are selected, respectively. The heavy density pollution sources located outside the urban area and the heavy density gaseous sources located in the center of the city are discussed, respectively.Under the condition of horizontal natural wind, the deposition process between buildings with different staggered ratios and the relationship between the distribution of heavy density gaseous pollutants in pedestrian areas and the building staggered ratios in the pedestrian areas were investigated.In this paper, firstly, the steady state of mercury source located outside the city block is simulated to study the influence of the distribution of building height and height on the diffusion of mercury vapor in the urban area.The simulation results show that the distribution of buildings with different height in urban blocks will promote the accumulation of high-altitude mercury pollution sources in pedestrian areas, and make the mercury concentration in pedestrian areas increase obviously, and with the increase of the ratio of buildings to buildings,The street with the highest mercury concentration value gradually approached to the mercury source, and the mercury mass flux in the pedestrian area of the street with higher building leeward was obviously higher than that in the pedestrian area on the leeward street of the lower building.Then unsteady simulation of toluene diffusion in the block under the action of urban wind is carried out with time line, and the relationship between toluene diffusion and time and the ratio of urban buildings to the difference between toluene diffusion and urban buildings is explored.The results showed that when the building height of the block was consistent, the time taken by toluene to spread to the downwind street was shorter than that when the building height was inconsistent, and when the building height of the block was not consistent,The concentration of toluene in the street at the higher building leeward was generally higher than that in the street at the lower building. When the building height was consistent, the toluene concentration in each street decreased with time, but when the building height was inconsistent, the concentration of toluene in the street decreased with time, but when the height of the building was not consistent,The toluene in the downwind streets even regrouped back into the pedestrian area; after a while, the toluene concentration in the street where the outbreak occurred was the highest in the block with a building staggered ratio of 0.4, followed by the block with the building disparity ratios of 0.6 and 0.8.The last block is a block with a staggered ratio of 0.2 and 0.Finally, the flow field in the water tank model of urban block is measured by using PIV particle image velocimetry system, which verifies the accuracy of computational fluid dynamics (CFD) in the study of urban block airflow organization.Based on the numerical simulation of steady and unsteady state, the diffusion law of heavy density gaseous pollutants in urban blocks with different distribution of buildings is studied in this paper.The results of the study provide a theoretical basis for the treatment of heavy density gaseous pollutants in the residential environment of urban blocks, which is beneficial to the determination of the specific location of polluted streets and the degree of pollution of different streets in urban areas.Has certain practical significance.
【學位授予單位】：湖南工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：X51;TU834

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本文編號：1729141