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Impact of street intersections on air quality in an urban environment

机译：街道十字路口对城市环境中空气质量的影响

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The impact of the street intersections on flow and gaseous pollutants from vehicles exhausts within urban canyons was numerically investigated using a computational fluid dynamics (CFD) model. Three-dimensional flow and dispersion of gaseous pollutants were modeled using standard k-ε turbulence model, which was numerically solved based on Reynolds-averaged Navier-Stokes equations by the commercial CFD code FLUENT. The concentration fields in the urban canyons were examined in three street configurations cases: (i) a regular-shaped intersection, (ii) T-shaped intersection and (iii) skew-shaped crossing intersection. Vehicle emissions were simulated as double line sources along the street. The numerical model was validated against wind tunnel results in order to optimize the turbulence model. Numerical predictions agreed reasonably with wind tunnel results. The results obtained indicate that the mean horizontal velocity was observed very small in the center near the lower region of street canyon. The lowest turbulent kinetic energy was found at the separation and reattachment points associated with the corner of the down part of the upwind and downwind buildings in the street canyon. The pollutant concentration at the upwind side in the regular-shaped street intersection was higher than that in the T-shaped and skew-shaped street intersections. Moreover, the results approve that the street intersections are important factor to predict the flow patterns and pollutant dispersion in street canyon.
机译：使用计算流体动力学（CFD）模型，对街道交叉路口对城市峡谷内车辆废气中的流量和气体污染物的影响进行了数值研究。使用标准k-ε湍流模型对气态污染物的三维流动和扩散进行建模，该模型基于Reynolds平均Navier-Stokes方程，通过商用CFD代码FLUENT进行数值求解。在三个街道配置情况下检查了城市峡谷中的集中场：（i）规则形状的交叉口，（ii）T形交叉口和（iii）倾斜形交叉口。车辆排放被模拟为沿街的双线排放源。针对风洞结果验证了数值模型，以优化湍流模型。数值预测与风洞结果基本吻合。获得的结果表明，在街道峡谷下部附近的中心，观测到的平均水平速度非常小。在与街道峡谷中上风和下风建筑物的下部的角相关的分离和重新连接点处发现了最低的湍动能。规则形街道交叉口上风侧的污染物浓度高于T形和倾斜形街道交叉口的污染物浓度。此外，研究结果表明，街道交叉口是预测街道峡谷的流型和污染物扩散的重要因素。

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