臺灣博碩士論文加值系統

本試驗主要在探討都市地形下，兩建築物形成的街谷所造成汙染擴散之影響。試驗利用環境風洞配合渦流產生器(spire)及粗糙元素(roughness elements)，模擬都市地形之迫近流場。
試驗使用垂直排放之煙囪對不同建築物形成的不同間距之街谷，與不同排放源高度探討不同排列方式對汙染物擴散之影響，將試驗結果與討論進行分析得以下之結論。
(1) 環境風洞配合渦流產生器粗糙元素及粗糙元素，模擬出所需之都市地形紊流邊界層，且指數律風速剖面之n值為0.27，符合Counihan(1975)實場研究結果之建議值。
(2) 當街谷間隔S較為狹窄，容易受建築物影響，街谷之上方，也會因後方建築物之阻擋，使流動朝上方回流造成濃度聚集的情形。街谷內的追蹤氣體之濃度較易累積且擴散較慢。當街谷間隔S較寬廣，街谷內之氣流有較大之流動性，因此追蹤氣體之濃度較易往下游擴散。
(3) 當前後排間距較小，而後排建築物高為2H時，由於氣流通過前排建築物已產生分離現象，在極短之距離又碰上後棟建築物產生分離現象，再加上受後排建築物之影響，使在後排建築物迎風面產生明顯之下切氣流，如此的交互作用之下，使追蹤氣體有明顯之抬升現象。

This study was to explore the dispersion characteristics of airborne pollutant around the set-up cayon. Experiment are conducted in the Environmental Wind Tunnel of Nation Taiwan Ocean University. Spire arrays roughness elements were deployed to simulate a turbulent boundary layer as the approaching flow. Cases of different building heights, different cayon spaces and source heighs are run in the experiments.Results are summarized as follows:
(1) The neutral atmospheric turbulent boundary layer flow was simulated as the approaching flow which had the power-law mean velocity profile with exponent n=0.27. This exponent value is within the range of urban type of atmospheric boundary layer flow proposed by Counihan(1975).
(2) When the canyons spacing becomes narrow,due to the the rear of the building of the barrier, the flow upward reflux causes aggregation concentration situation. The concentration of trace gases accumulate more readily around the canyon. As canyon spacing becomes broader, airflows in the canyon are the greater mobility. Therefore trace concentrations are transported in downstream.
(3) When the canyon spacing becomes small, while the rear building with height 2H(H is the front building height),a significant uplift flow phenomenon has occurred. This caused the tracer pollution accumulating around the apper position of rear building.

摘要 I
ABSTRACT II
目次 III
圖目次 V
符號說明 X
第一章　導論 1
1-1　前言 1
1-2　研究目的 1
1-3　文獻回顧 1
第二章　風洞試驗之基本理論分析 3
2-1　中性大氣紊流邊界層之平均風速剖面 3
2-2　中性大氣紊流邊界層之風洞試驗模擬 5
2-2-1　相似性法則 5
2-2-2　渦流產生器(spire)之設計原理 6
2-2-3　粗糙元素(roughness elements)之設計原理 7
2-3　高斯擴散理論 8
2-4 濃度因次分析 9
第三章　試驗儀器與量測 12
3-1　試驗儀器 12
3-1-1　大氣環境風洞介紹 12
3-1-2　風場量測儀器 13
3-1-3　濃度場量測之儀器 13
3-2　試驗設計與方法 14
3-2-1　模型設計 14
3-2-2　追蹤氣體之設計 14
3-2-3　採集斷面設計 15
第四章　試驗結果與討論 16
4-1　迫近流場之模擬結果 16
4-2　濃度擴散分佈特性分析與討論 16
4-2-1　後排建築物高為1.5H之濃度擴散分佈 16
4-2-2　後排建築物高為2H之濃度擴散分佈 17
4-2-3　後排建築物高度變化之垂直向濃度影響 18
4-2-4　改變煙囪之垂直向濃度影響 18
4-2-5　各斷面擴散尺度之變化 18
4-2-6 排放源下游各斷面最大濃度之變化 18
4-3　後排建築物表面濃度分佈特性分析與討論 19
第五章　結論 20
參考文獻 21
附圖 23
謝誌 102

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