Amini Seyedmorteza, Ahangar Faraz Enayati, Heist David K, Perry Steven G, Venkatram Akula
Department of Mechanical Engineering, University of California, Riverside, CA 92521, USA.
Atmospheric Modeling and Analysis Division, National Exposure Research Laboratory, MD-81, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
Atmos Environ (1994). 2018;186:189-197. doi: 10.1016/j.atmosenv.2018.04.058.
This paper presents an analysis of data from a wind tunnel (Heist et al., 2009) conducted to study dispersion of emissions from three depressed roadway configurations; a 6 m deep depressed roadway with vertical sidewalls, a 6 m deep depressed roadway with 30° sloping sidewalls, and a 9 m deep depressed roadway with vertical sidewalls. The width of the road at the bottom of the depression is 36 m for all cases. All these configurations induce complex flow fields, increase turbulence levels, and decrease surface concentrations downwind of the depressed road compared to those of the at-grade configuration. The parameters of flat terrain dispersion models are modified to describe concentrations measured downwind of the depressed roadways. In the first part of the paper, a flat terrain model proposed by van Ulden (1978) is adapted. It turns out that this model with increased initial vertical dispersion and friction velocity is able to explain the observed concentration field. The results also suggest that the vertical concentration profiles of all cases under neutral conditions are best explained by a vertical distribution function with an exponent of 1.3. In the second part of the paper, these modifications are incorporated into a model based on the RLINE (Snyder et al., 2013) line-source dispersion model. While this model can be adapted to yield acceptable estimates of near-surface concentrations (z< 6m) measured in the wind tunnel, the Gaussian vertical distribution in RLINE, with an exponent of 2, cannot describe the concentration at higher elevations. Our findings suggest a simple method to account for depressed highways in models such as RLINE and AERMOD through two parameters that modify vertical plume spread.
本文对风洞实验数据进行了分析（Heist等人，2009年），该实验旨在研究三种凹陷式道路结构排放物的扩散情况；一种是带有垂直侧壁的6米深凹陷式道路，一种是带有30°倾斜侧壁的6米深凹陷式道路，还有一种是带有垂直侧壁的9米深凹陷式道路。在所有情况下，凹陷底部道路的宽度均为36米。与地面配置相比，所有这些结构都会引发复杂的流场，增加湍流水平，并降低凹陷道路下游的地面浓度。对平坦地形扩散模型的参数进行了修改，以描述凹陷道路下游测得的浓度。在本文的第一部分，采用了van Ulden（1978年）提出的平坦地形模型。结果表明，该模型通过增加初始垂直扩散和摩擦速度，能够解释观测到的浓度场。结果还表明，在中性条件下，所有情况的垂直浓度剖面最好用指数为1.3的垂直分布函数来解释。在本文的第二部分，将这些修改纳入了基于RLINE（Snyder等人，2013年）线源扩散模型的模型中。虽然该模型可以进行调整，以给出风洞中测得的近地表浓度（z<6米）的可接受估计值，但RLINE中指数为2的高斯垂直分布无法描述较高海拔处的浓度。我们的研究结果提出了一种简单的方法，通过修改垂直羽流扩散的两个参数，在RLINE和AERMOD等模型中考虑凹陷式高速公路的影响。
