臺灣博碩士論文加值系統

本研究之主要目的為建立不同粒徑之懸浮微粒軌跡追蹤模擬方法，比較開放式 (opened) 及交錯式 (staggered) 等兩種建築物群排列方式之三維度環境風場及懸浮微粒之傳輸行為與排除效率。本研究對三維度建築物群之環境風場數值分析，係採用有限體積法(finite volume method) 離散控制方程式，以SIMPLE法耦合速度及壓力，使得整個流場符合質量守恆及動量守恆，同時結合大渦模擬 (large eddy simulation，LES) 紊流模式、亞格點尺度應力模式 (subgrid scale stress model，SGS) 與邊牆函數 (wall function) 來模擬紊流流場。本研究並以拉格蘭日 (Lagrangian) 觀點之氣懸微粒軌跡追蹤模式模擬建築物群之懸浮微粒軌跡傳輸行為。微粒軌跡追蹤模式除了計算傳統的阻力與重力外，又增加考慮Saffman升力與布朗運動作用力對於微粒的影響。本研究首先進行微粒釋放粒數之敏感度分析，結果當微粒釋放總粒數超過1萬顆以上時，可確保氣懸微粒質量濃度與粒數濃度之精確度。
在比較開放式街谷與交錯式街谷的行人風場後，結果指出在開放式建築物群中微粒懸浮於直流區之PM10濃度高於尾流區約10％，且PM10之微粒排除效率亦比PM1及PM2.5較為不佳。在交錯式建築物群中微粒懸浮於直流區則較尾流區高出約70％。在微粒排除效率方面，PM10在兩種建築物排列方式中都較PM2.5及PM1佳，交錯式又較開放式顯著。
在微粒傳輸過程中由於大微粒具有較大的慣性衝擊與重力沈降能力，當大微粒傳輸至建築物後方時，較易離開因建築物排列方式所造成的渦流，小微粒因放鬆時間小比大微粒需要更久的時間沉降於地面且會在隨著次要氣流或是環境流場所產生的漩渦等影響來回地盤旋而滯留於尾流區，故造成交錯式建築物群的尾流區內PM2.5及PM1的微粒質量濃度累積最甚。

The main objectives of this study are to establish trajectory tracking technique for different particle sizes and to compare the effects of different building layout (i.e., opened and staggered street canopies) on turbulent flow field and particulate matter transport in urban street canopies.
To simulate the three-dimensional turbulent flow field under different urban street canopies, we select the finite volume method to discretize the governing equations of our numerical model. SIMPLE scheme is used to adjust flow field to satisfy the continuity equation. Large eddy simulation (LES) together with the subgrid-scale stress model (SGS) and the wall function are adopted to model the turbulence flow field in the study. The Lagrangian particle trajectory tracking technique is adopted to investigate particulate matter transport behavior in urban street canopies. The effects of the drag force, gravitational force, Brownian motion, and Saffman lift force on particles are all considered in the particle tracking technique. A sensitive analysis is firstly conducted to assess how many particles are necessary to be released in the simulated 3-D turbulent flow field for maintaining in a stable concentration profile. The analysis indicates that as the released particles are more than 10000, the particle and number concentration distributions approach to a steady profile.
The simulated results show that, in the opened street canopy at the pedestrian wind airflow range, PM10 concentration in the gap area is 10% higher than that in the wake zone. However, it increases to 70% in the staggered street canopies. Also, in the gap area, the removal efficiency for PM2.5 and PM1 is better than that for PM10, especially in the staggered street canopies.
The larger particles are easier to deposit than smaller ones. Once the large particles are transported to the vortex region behind the buildings, it is hard for them to escape from the region. The smaller particles need longer time to deposit. In the staggered street canopies, these small particles would follow low-velocity airflow and wander in the wake zone. This phenomenon results in accumulations of PM2.5 and PM1 in this region.

摘 要………………………………………………………………I
Abstract………………………………………………………………III
目 錄………………………………………………………………V
表 目 錄……………………………………………………………VII
圖 目 錄…………………………………………………………VIII
第一章、緒論……………………………………………………………1
1.1前言…………………………………………………………………1
1.2 研究動機……………………………………………………………2
1.3 前人研究……………………………………………………………3
第二章、環境風場與微粒軌跡模式……………………………………6
2.1 三維度建築物群之環境風場………………………………………6
2.1.1環境風場基本控制方程式………………………………………6
2.1.2紊流模式介紹……………………………………………………7
2.1.3環境風場之邊界條件……………………………………………11
2.1.4數值方法…………………………………………………………11
2.2微粒軌跡追蹤模式…………………………………………………12
2.2.1三維度拉格蘭日微粒追蹤模式…………………………………13
2.2.2微粒追蹤之基本假設……………………………………………16
2.2.3微粒運動之起始與邊界條件……………………………………16
2.2.4數值方法…………………………………………………………17
2.3 微粒濃度計算方法………………………………………………17
2.3.1 煙團顆粒法 (puff-particle method) ……………………17
第三章、模式驗證……………………………………………………23
3.1 開放式建築物群紊流模式驗證…………………………………24
3.2 開放式與交錯式建築物群紊流模式驗證………………………24
第四章、模式應用案例介紹及網格敏感度分析……………………31
4.1 模式應用案例介紹………………………………………………31
4.2建築物群之環境風場流況………………………………………31
4.3 建築物群之微粒場概述…………………………………………32
4.3.1微粒質量濃度之計算……………………………………………33
4.4網格敏感度分析……………………………………………………34
4.5釋放微粒數之敏感度分析…………………………………………35
第五章、模擬結果與討論……………………………………………43
5.1 開放式建築物群 (opened street canopies) ………………43
5.1.1流場分析………………………………………………………43
5.1.2懸浮微粒傳輸模擬結果………………………………………43
5.1.3 PM10微粒質量濃度比較………………………………………44
5.1.4 粒徑分佈比較…………………………………………………44
5.1.5 街谷直流區與尾流區微粒質量濃度PM10/PM2.5/PM1之排除
比 較…………………………………………………………45
5.2交錯式建築物群 (staggered street canopies) ……………46
5.2.1 流場分析………………………………………………………46
5.2.2懸浮微粒傳輸模擬結果………………………………………47
5.2.3 PM10微粒質量濃度比較………………………………………47
5.2.4粒徑分佈比較……………………………………………………48
5.2.5 街谷直流區與尾流區微粒質量濃度PM10/PM2.5/PM1之排除比
較………………………………………………………………48
5.3開放式與交錯式建築物群之比較………………………………49
5.3.1 PM10微粒質量濃度比較………………………………………49
5.3.2 街谷直流區與尾流區微粒質量濃度PM10/PM2.5/PM1之排除比
較………………………………………………………………50
第六章、結論與建議…………………………………………………69
6.1 結論………………………………………………………………69
6.2 建議………………………………………………………………70
參考文獻 ……………………………………………………………71

1.Ahmadi, G. and Li, A., 2000, Computer simulation of particle transport and deposition near a small isolated building, J. of Wind Engineering and Industrial Aerodynamics, 84, 23-46.
2.Balaras, E., Benocci, C. and Piomelli, U., 1995, Finite-difference computations of high Reynolds number flows using the dynamic subgrid-scale model., Theoretical and Computational Fluid Dynamics, 7, 207-216.
3.Chang, T.J. and Yen, B.C., 1998, Gravitational fall velocity of sphere in viscous fluid, J. of Engineering Mech., ASCE, 124, 1193-1199.
4.Chang, T.J., Huang, M.Y., Wu, Y.T. and Liao, C.M., 2003, Quantitative prediction of traffic pollutant transmission into buildings, J. of Environment Sci. and Health, A38, 999-1014.
5.Chang, T.J. and Wu, Y.T., 2003., Wind-driven rain trajectories around street canopies., J. of the American Water Resources Association, 39, 545-562.
6.Chang, T.J., 2002, Numerical evaluation of the effect of traffic pollution on indoor air quality of a naturally ventilated building, J. of Air & Waste Manage. Assoc., 52, 1043-1053.
7.Cheng Y., Lien, F.S., Yee, E. and Sinclair, R., 2003, A comparison of large Eddy simulations with a standard k-ε Reynolds-averaged Navier-Stokes model for the prediction of a fully developed turbulent flow over a matrix of cubes., J. of Wind Engineering and Industrial Aerodynamics, 91, 1301-1328.
8.Clift, R., Grace, J.R. and Weber, M.E., 1978, Bubbles drops and particles, Academic Press, New York.
9.Deardorff, J.W., 1970, A numerical study of three-dimensional turbulent channel ow at large Reynolds numbers., J. of Fluid Mech., 41, 453-480.
10.De Haan, P. and Rotach, M.W., 1995, A puff-particle dispersion model., J. of Environment and pollution, 5, 350-359.
11.Hanna, S.R., Tehranian, S., Carissimo, B. and Macdonald, R.W., 2002, Comparisons of model simulations with observations of mean flow and turbulence within simple obstacle arrays., J. of Atmospheric Environment 36, 5067-5079.
12.Honey, L.F. and McQuitty, J.B., 1979, Some physical factors affecting dust concentrations in pig facility., Can. Agric. Eng, 21, 9-14.
13.Hsieh, C.I., Siqueira, M., Katul, G. and Chu, C.R., 2003, Predicting scalar source-sink and flux distributions within a forest canopy using a 2-D Lagrangian stochastic dispersion model., Boundary-Layer Meteorology, 109, 113-138.
14.Kim, J.J. and Baik, J.J, 2004, A numerical study of the effects of ambient wind direction on flow and dispersion in urban street canyons using the RNG k-ε turbulence model., Atmospheric Environment, 38, 3039-3048.
15.Li, C.S. and Lin, C.H., 2002, PM1/PM2.5/PM10 Characteristics in the Urban Atmosphere of Taipei, J. of Aerosol Science and Technology, 36, 469-473
16.Li, A. and Ahmadi, G., 1992, Dispersion and deposition of spherical particles from point sources in a turbulent channel flow., J. of Aerosol. Sci. Tech., 16, 209-226.
17.Lu, S.Y., 1996, Narrowest particle size distributions in aerosol processes, J. of Chin. Inst. Chem. Eng, 27, 71-78
18.Lu, W., Howarth, A.T., Adam, N. and Riffat, S.B., 1996, Modeling and measurement of airflow and aerosol particle distribution in a ventilated two-zone chamber., Building and Environment, 31, 417-423.
19.Panton, R.L., 1984, Incompressible Flow., A Wiley-Interscience publication.
20.Raza, S., Avila, R. and Cervantes, J., 2002, A 3D Lagrangian particle model for the atmospheric dispersion of toxic pollutants., J. of Energy Research, 26, 93-104.
21.Rao, S.S., 2002, Applied numerical methods for engineers and scientists, Prentice Hall, New Jersey.
22.Rodi, W., 1997, Comparison of LES and RANS calculations of the flow around bluff bodies., J. of Wind Eng. Ind. Aero., 69-71, 55-75.
23.Smagorinsky, J., 1963, General circulation experiments with the primitive equations I, The basic experiment, Mon. Weather Rev., 91, 99–164.
24.Xia, J.Y. and Leung, D.Y.C., 2001a, Pollutant dispersion in urban street canopies., Atmospheric Environment, 35, 2033-2043.
25.Xia, J.Y. and Leung, D.Y.C., 2001b, A concentration correction scheme for Lagrangian particle model and its application in street canyon air dispersion modeling., Atmosphere Environment, 35, 5779-5788.
26.Yamada, T. and Bunker, S., 1988, Development of a nested grid second moment turbulence closure model and application to the 1982 ASCOT brush creek data simulation., J. of Applied Meteorology, 27, 562-578.
27.Zhang, W. and Chen, Q., 2000, Large eddy simulation of indoor airflow with a filtered dynamic subgrid scale model. Int., J. of Heat Mass Transfer, 43, 3219-3231.
28.朱佳仁，2002。「環境流體力學」, 科技圖書。
29.黃俊強，2001，「低層建築物環境風場與風載之數值研究」，國立台灣大學農業工程學研究所碩士論文。
30.郭鴻興，2001，「以計算流體動力學分析自然通風低層建築物之通風特性」，國立台灣大學農業工程學研究所碩士論文。
31.吳毓庭，2003，「紊流大渦模擬在二維與三維設施環境問題之研究」，國立台灣大學生物環境系統工程學研究所碩士論文。
32.謝怡芳，2004，「三維度紊流大渦模擬在多區間建築物室內環境風場之應用研究」，國立台灣大學生物環境系統工程學研究所碩士論文。
33.高宏名，2004，「以三維度微粒軌跡追蹤模式研析多區間建築物室內懸浮微粒傳輸行為」，國立台灣大學生物環境系統工程學研究所碩士論文。
34.梁鳳文，2004，「以歐氏-拉氏法模擬煙流粒子在建築物尾流區中的擴散」，國立中央大學土木工程學研究所碩士論文。