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Numerical Simulation of Flow past Discrete Broadleaf Trees
|關鍵字:||數值模擬;Numerical simulation;風洞試驗;行道風;闊葉樹;Wind tunnel measurement;Pedestrian wind;Broadleaf tree.||出版社:||土木工程學系所||引用:|| Raupach, M.R., Antonia, R.A. and Rajagopalan, S. (1991), “Rough-wall turbulent boundary layers,” Applied Mechanics Review, Vol. 44, pp. 1-25.  Gardiner, B.A. (1994), “Wind and windforces in a plantation spruce forest,” Boundary-Layer Meteorology, Vol. 67, pp. 161-186.  Cionco, R.M. (1985), “On modeling canopy flow coupled to the surface boundary layer,” 17th Conference Agricultural and Forest Meteorology and 7th Conference Biometeorology and Aerobiology, pp. 116-119.  Mihailovic, D.T., Lalic, B., Rajkovic, B. and Arsenic, I. (1999), “A roughness sublayer wind profile above non-uniform surface,” Boundary-Layer Meteorology, Vol. 93, No. 3, pp. 425-451.  Raupach, M.R., Coppin, P.A. and Legg, B.J. (1986), “Experiments on scalar dispersion within a model plant canopy. Part I: The turbulence structure,” Boundary-Layer Meteorology, Vol. 35, pp. 21-52.  Massman, W. (1987), “A comparative study of some mathematical models of the mean wind structure and aerodynamic drag of plant canopies,” Boundary-Layer Meteorology, Vol. 40, pp. 179-197.  Novak, M.D., Warland J.S., Orchaansky, A.L., Ketler, R. and Green, R. (2000), “Wind tunnel and field measurements of turbulent flow in forests. Part I: Uniformly thinned stands,” Boundary-Layer Meteorology, Vol. 95, pp. 457-495.  Boldes, U., Colman, J. and Maranon D.L.J. (2001), “Field study of the flow behind single and double row herbaceous windbreaks,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 89, pp. 665-687.  Flesch, T.K. and Wilson, J.D. (1999), “Wind and remnant tree sway in forest cutblocks. I. Measured winds in experimental cutblocks,” Agricultural and Forest Meteorology, Vol. 93, pp. 229-242.  Shaw, R.H. and Schumann, U. (1992), “Large-eddy simulation of turbulent flow above and within a forest,” Bound-Layer Meteorology, Vol. 61, pp. 47-64.  Wilson, J.D. and Flesch, T.K. (1999), “Wind and remnant tree sway in forest cutblocks. III. A windflow model to diagnose spatial variation,” Agricultural and Forest Meteorology, Vol. 93, pp. 243-258.  Raynor, G.S. (1971), “Wind and temperature structure in a conferous forest and a contiguous field,” Forest Science, Vol. 17, pp. 351-363.  Sladek, I., Bodnar, T. and Kozel, K. (2007), “On a numerical study of atmospheric 2D and 3D-flows over a complex topography with forest including pollution dispersion,” Journal of Wind Engineering and Industrial Aerodynamic, Vol. 95, pp. 1424-1444.  Yamaguchi, A., Enoki, K. and Ishihara, T. (2009), “A generalized canopy model for the wind prediction in the forest and the urban area” The 7th Asia-Pacific Conference on Wind Engineering, T2-A5, Taipei, Taiwan.  Maruyama, T. (2008), “Large eddy simulation of turbulent flow around a windbreak,” Journal of Wind Engineering and Industrial Aerodynamic, Vol. 96, pp. 1998-2006.  Brunet, Y., Finnigan, J.J. and Raupach M.R. (1993), “A wind tunnel study of air flow in waving wheat: Single-point velocity statistics,” Boundary-Layer Meteorology, Vol. 81, pp. 95-132.  Raupach, M.R. (1992), “Drag and drag partition on rough surfaces,” Boundary-Layer Meteorology, Vol. 60, pp. 375-385.  Grigoriadis, D.G.E., Bartzis J.G. and Goulas, A. (2004), “Efficient treatment of complex geometries for large eddy simulations of turbulent flows,” Computers and Fluids, Vol. 33, No. 2, pp. 201-222.  Song, C. and Yuan, M. (1988), “A weakly compressible flow model and rapid convergence method,” ASME Journal of Fluids Engineering, Vol. 110, No. 4, pp. 441-455.  Smagorinsky, J. (1963), “General circulation experiments with primitive equations,” Month Weather Review, Vol. 91, pp. 99-164, Cincinnati, Ohio.  MacCormack, R. (1969), “The effect of viscosity in hyper-velocity impact cratering,” AIAA paper, pp. 69-354.  Courant, R., Friedrichs, K.O. and Lewy, H. (1967), “On the partial difference equations of mathematical physics,” IBM Journal, pp. 215-234. Shaw與Schumann  方偉德(2004)，“大氣與森林之間紊流流場之風洞實驗”，國立中央大學土木工程研究所碩士論文，桃園。  關德新、朱廷曜、韓士杰(2001)，“單株樹的阻力係數模式”，林業科學，第37卷，第6期，第11-14頁。  楊峻(2011)，“通過獨立針葉樹木之風場模擬研究”，國立中興大學土木工程研究所碩士論文，台中。  楊純明(2009)，“農作物生長的量測與追蹤”，農委會農業試驗所作物組期刊論文，第80期，第33-36頁。  黎益肇(2009)，“風場通透樹木特性模式之建立與應用”，內政部建築研究所自行研究報告。  蔡惠文(1996)，“均勻來流中二維矩柱之流場模擬”，國立中興大學土木工程研究所碩士論文，台中。||摘要:||
Planting trees in an open area can generally slow down the near-ground wind speed thus becomes an important way in pedestrian wind planning. At the preliminary design stage, to analyze the flow past discrete trees, wind tunnel model experiments are mostly employed. Besides the amount of human labor and time required in the execution of experimental work, however, technical difficulties (such as the scale effect) are generally encountered. In contrast, the adoption of numerical simulations can be another alternative for the flow analysis. Accordingly, the study is to establish a numerical model, capable of correctly predicting flows past discrete broadleaf trees that can be handily adopted in the governing equations proposed by previous researchers to explore a relationship to properly describe the physical effect of trees so as to provide a handy tool for pedestrian wind analysis during the preliminary design for local wind environments.
The study concentrates on the problem of the banyan trees which subject to broadleaf plants. In addition to numerical computations, wind tunnel measurements were also performed to guide and confirm the numerical simulations. In the wind tunnel experiments, Cobra Probe was adopted to measure the downstream cross-sectional mean and root-mean-square velocity profiles. Besides, the variation of the tree parameter was obtained as a function of the tree body density and width. A weakly-compressible-flow method is used in the numerical simulations by adding a source term in the momentum equations to reflect the physical effect of trees. Furthermore, by using a try-and-error method to compare with the measurement profiles corresponding to a prescribed thickness and volume density of trees, the tree parameter that lead to the best agreement between the measurement and calculated profiles was then obtained.
The results showed that basically the tree parameter increased with increases of both the tree body density and varied significantly with the tree body widths. Moreover, based on the calibrated relationship of the tree factor, numerical computations were further performed to simulate flow past an isolated tree and dual trees. The predicted downstream wind speed profiles showed good agreements compared to the measurement results.
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