臺灣博碩士論文加值系統

本試驗主要透過環境風洞實驗探討都市地形之中性大氣紊流邊界層內下降型街谷在不同建物高差、街谷間距、汙染源排放高度的不同條件下之汙染擴散特性。
實驗結果顯示：
(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之中性大氣紊流邊界層，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) 當街谷間距較小時，汙染濃度容易滯留於街谷內。當街谷間隔加大時，街谷上方之汙染往下游擴散。
(3) 街谷下降較大(後排建物高度較低)時，街谷之汙染擴散尺度較大。
(4) 當街谷間距增加時，建物之高度改變對擴散影響將不顯著。

The study was to investigate the dispersion of elevated source which discharged vertically into the step down canyon. The urban type of neutral atmospheric turbulent boundary layer was simulated in the wind tunnel. The mean velocity profile was expressed in power-law with the exponent n=0.27. The simulation results are found in agreement with the results proposed by Counihan(1975). Measurement results show that the pollutants are accumulated in the street canyon when the width of canyon becomes narrow. As the width of canyon is wider, the pollutants diffuse better. When the step down steepness for canyon increases, the dispersion becomes better in the canyon. The effect on the pollution dispersion for canyon width is more significant than that of for canyon step down steepness.

摘要 I
ABSTRACT II
目次 III
圖目次 V
符號說明 IX
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風場特性 3
2-1-1　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　渦流產生器(spire)之設計原理 5
2-2-2　粗糙元素(roughness elements)之設計原理 6
2-2-3　相似性法則 6
2-3　濃度因次分析 8
2-4　高斯擴散理論 10
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　採集斷面設計 15
3-2-3　追蹤氣體設計 15
第四章　試驗結果與討論 16
4-1　迫近流場模擬結果 16
4-2　風場特性分析 16
4-3　濃度場擴散分佈之特性分析 16
4-3-1　後排建物高為0.5H之濃度擴散分析 17
4-3-2　後排建物高為0.75H之濃度擴散分析 18
4-3-3　後排建物高度變化之垂直剖面濃度比對分析 18
4-3-4　煙囪(排放源)變化之垂直剖面濃度比對分析 19
4-3-5　各斷面擴散尺度之變化分析 19
4-4　高斯擴散理論分析與討論 19
第五章　結論 21
參考文獻 22
附圖 24
謝誌 97

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