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Title: | 非均勻地形之紊流擴散模擬 Numerical Simulation of Turbulent Diffusion over Non-homogeneous Terrain |
Authors: | Tsung-Han Tsai 蔡宗翰 |
Advisor: | 謝正義 |
Keyword: | 二維擴散,標準k-ε紊流模式,流場阻礙物,森林密度,市蓋,混合層高度,濃度累積量,濃度混合效率, two-dimensional turbulence diffusion,standard k-ε model,forest density,mixing layer height,diffusion efficiency, |
Publication Year : | 2006 |
Degree: | 碩士 |
Abstract: | 本文以二維擴散方程為基礎,模擬穩定邊界層情況下被動擴散情形。並以二維標準k-ε紊流模式(Standard k-ε model)計算建立風場之數值模型,探討水田對於其下風處之流場阻礙物,分別為(1)單棟低矮建築物與(2)森林或市蓋(urban canopy)時,水汽在穩定邊界層內風場與被動擴散傳輸情形。本模式包含水平風速、垂直風速、總壓力、紊流動能、紊動能消散率、紊流黏滯係數、濃度等變數。
在本研究中,吾人將森林分為高、中、低密度三種等級。研究結果發現:高、中密度的森林造成的流場性質,與低密度時明顯不同。而物質紊流擴散的混合層高度與森林(或市蓋)密度成正比。流場阻礙物周遭的濃度累積量,正比於森林(或市蓋)密度。另外,不同的森林(或市蓋)密度,也造成流場局部不同的濃度混合效率。 The present study is based on a two-dimensional turbulence diffusion model, in which the passive-mixing in neutral atmosphere boundary layer is simulated. In the numerical model, two-dimensional standard k-ε turbulent model is employed to simulate the flow field. The passive transportation of water vapor passing by solid structure and permeable structures is discussed. The parameters in the present numerical model include horizontal wind velocity, vertical wind velocity, total pressure, turbulent kinetic energy, turbulent dissipation rate, turbulent viscosity, and water vapor concentration. In the research, forest density is classified into three levels: high, medium and low. The result shows that the characteristics of flow field in high and medium dense forest are obviously different from that in low dense forest. The height of mixing layer and the aggregate value of vapor concentration grow with the forest density. Furthermore, density levels of the forest also cause different diffusion effect in the flow field. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/33719 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 生物環境系統工程學系 |
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File | Size | Format | |
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ntu-95-1.pdf Restricted Access | 1.53 MB | Adobe PDF |
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