Department of Environmental Technology and Management, Kuwait University, P.O. Box 5969, Safat, Kuwait.
J Expo Sci Environ Epidemiol. 2012 Sep;22(5):502-15. doi: 10.1038/jes.2012.59. Epub 2012 Jul 4.
To assist validation of numerical simulations of urban pollution, air quality in a street canyon was investigated using a wind tunnel as a research tool under neutral atmospheric conditions. We used tracer gas techniques from a line source without buoyancy. Ethylene (C(2)H(4)) was used as the tracer gas. The street canyon model was formed of six parallel building rows of the same length. The flow and dispersion field was analyzed and measured using a hot-wire anemometer with split fiber probe and fast flame ionization detector. The diffusion flow field in the boundary layer within the street canyon was examined at different locations, with varying building orientations (θ=90°, 112.5°, 135° and 157.5°) and street canyon aspect ratios (W/H=1/2, 3/4 and 1) downwind of the leeward side of the street canyon model. Results show that velocity increases with aspect ratio, and with θ>90°. Pollutant concentration increases as aspect ratio decreases. This concentration decreases exponentially in the vertical direction, and decreases as θ increases from 90°. Measured pollutant concentration distributions indicate that variability of building orientation and aspect ratio in the street canyon are important for estimating air quality in the canyon. The data presented here can be used as a comprehensive database for validation of numerical models.
为了协助验证城市污染的数值模拟，本研究采用中性大气条件下的风洞作为研究工具，调查了街道峡谷中的空气质量。我们使用无浮力的线状源示踪气体技术。乙烯（C(2)H(4)）被用作示踪气体。街道峡谷模型由六个相同长度的平行建筑行组成。使用带有分裂光纤探头的热线风速仪和快速火焰离子化探测器分析和测量流动和扩散场。在街道峡谷模型背风侧的不同位置，研究了不同建筑方位（θ=90°、112.5°、135°和 157.5°）和街道峡谷纵横比（W/H=1/2、3/4 和 1）下边界层内的扩散流场。结果表明，速度随纵横比和θ>90°而增加。污染物浓度随纵横比的减小而增加。该浓度在垂直方向上呈指数衰减，并且随着θ从 90°增加而减小。测量的污染物浓度分布表明，街道峡谷中建筑物方位和纵横比的变化对估算峡谷内的空气质量很重要。这里提供的数据可作为验证数值模型的综合数据库。
