A wind-tunnel study of windbreak drag

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	A wind-tunnel study of windbreak drag
	Guan, DX; Zhang, YS; Zhu, TY; Guan, DX, Chinese Acad Sci, Inst Appl Ecol, Shenyang 110016, Peoples R China
刊名	AGRICULTURAL AND FOREST METEOROLOGY
	2003
卷号	118 期号:1-2 页码:75-84
关键词	Realistic Windbreak Two-dimensional Windbreak Optical Porosity Aerodynamic Porosity Drag Coefficient
ISSN号	0168-1923
英文摘要	Drag coefficient is an important index of the wind protection effect of a windbreak. Although there have been many studies on this, there are very few with direct measurements, especially those on realistic windbreaks. We conducted wind-tunnel experiments on simulated models of narrow and realistic windbreaks with different porosities. The surface boundary layer on the wind-tunnel floor was simulated with a thickness of 600 mm. The model, with height (H) of 100 mm, was immersed in the simulated surface boundary layer during measurements. The ratio of the model height to roughness length of the surface (H/z(0)) was 774. Two indices, optical porosity (beta) and aerodynamic porosity (alpha), were used. The bleed wind speed of the model was measured to calculate aerodynamic porosity. The relative bleed speed was generally lower at the canopy crown-and higher at the bottom surface. Dense model canopy had smaller standard deviation (S.D.) in aerodynamic porosity along the crosswind direction. The relationship between alpha and beta resulted in alpha = beta(0.4) for realistic windbreak models. The divergence of alpha and beta was largest near 0.5 and 0.2, respectively and then decreased as the windbreak became denser or looser. The drag (D) and drag coefficient (C-d) of the models decreased with increasing porosity. The model C-d remained nearly constant within the range of Reynolds number measured in this study. The resultant C-d of our realistic model was lower than that of other studies using two-dimensional windbreaks with the same optical porosity. Our empirical relationship between C-d and alpha (i.e. C-d = 1.08(1 - alpha(1.8))) agreed well with that of two-dimensional windbreaks reported in the literature, suggesting that a was a better measure as porosity index than Beta. (C) 2003 Elsevier Science B.V. All rights reserved.
学科主题	Agronomy ; Forestry ; Meteorology & Atmospheric Sciences
语种	英语
WOS记录号	WOS:000184237300005
公开日期	2011-09-23
内容类型	期刊论文
源URL	[http://210.72.129.5/handle/321005/55389]
专题	沈阳应用生态研究所_沈阳应用生态研究所
通讯作者	Guan, DX, Chinese Acad Sci, Inst Appl Ecol, Shenyang 110016, Peoples R China
推荐引用方式 GB/T 7714	Guan, DX,Zhang, YS,Zhu, TY,et al. A wind-tunnel study of windbreak drag[J]. AGRICULTURAL AND FOREST METEOROLOGY,2003,118(1-2):75-84.
APA	Guan, DX,Zhang, YS,Zhu, TY,&Guan, DX, Chinese Acad Sci, Inst Appl Ecol, Shenyang 110016, Peoples R China.(2003).A wind-tunnel study of windbreak drag.AGRICULTURAL AND FOREST METEOROLOGY,118(1-2),75-84.
MLA	Guan, DX,et al."A wind-tunnel study of windbreak drag".AGRICULTURAL AND FOREST METEOROLOGY 118.1-2(2003):75-84.