School of Environment and Architecture, University of Shanghai for Science and Technology, No.516, Jungong Road, Yangpu District, Shanghai, 200093, China.
Natural Science Center, Kim Il Sung University, Taesong District, Pyongyang, Democratic People's Republic of Korea.
Environ Sci Pollut Res Int. 2022 Dec;29(59):89358-89386. doi: 10.1007/s11356-022-21827-1. Epub 2022 Jul 18.
In general, urban canyons are the areas most clearly affected by traffic pollutants since the ability of the canyon to self-ventilate is inhibited due to blockage of buildings or other urban structures. However, previous studies have aimed to improve the pedestrian-level wind speed with void deck in single buildings or short canyons. This study investigated the effects of void deck height and location, and the building height on the airflow field and the traffic pollutant diffusion in a long canyon with L/H = 10, validated by wind-tunnel experiment data. The results show that the void decks have a significant effect on the airflow and pollutant distribution inside the canyon. Air exchange rates (ACH) of the canyons with the void deck are much larger than that of regular canyons, and the perturbation changes of turbulence (ACH') decrease. For the windward void deck, purging flow rate (PFR) and normalized net escape velocity (NEV*) increase by 6.4 times compared to the regular canyon, and for the leeward void deck, increase by 13 times. In particular, when the void decks are at both buildings, they are increased by 38.3 times. Also, for the canyons with the void deck, traffic pollutants are removed out of the canyon by the strong airflow through the void deck. Therefore, unlike the regular canyons, as the void deck and the building height increases, the strength of the airflow through the void deck becomes stronger, and as a result, the mean pollutant concentration is significantly reduced at both walls and the pedestrian respiration level. The mean pollutant concentration on the wall of the building with the void deck and on the pedestrian respiration plane close to it is near zero. These findings can help ease traffic pollution inside the street canyons composed of high-rise buildings, especially in tropical cities.
一般来说，城市峡谷是受交通污染物影响最明显的区域，因为建筑物或其他城市结构的阻塞会抑制峡谷的自通风能力。然而，以前的研究旨在通过在单栋建筑或短峡谷中设置架空层来提高行人高度处的风速。本研究通过风洞实验数据验证了，在 L/H=10 的长峡谷中，研究了架空层高度和位置以及建筑物高度对气流场和交通污染物扩散的影响。结果表明，架空层对峡谷内的气流和污染物分布有显著影响。带架空层的峡谷的空气交换率（ACH）远大于常规峡谷，且湍流通量的扰动量（ACH'）减小。对于迎风架空层，吹扫流量（PFR）和归一化净逃逸速度（NEV*）比常规峡谷增加了 6.4 倍，对于背风架空层，增加了 13 倍。特别是当架空层位于两栋建筑物时，增加了 38.3 倍。此外，对于带架空层的峡谷，由于强气流通过架空层，交通污染物被从峡谷中排出。因此，与常规峡谷不同，随着架空层和建筑物高度的增加，通过架空层的气流强度增强，结果是在两侧墙壁和行人呼吸高度处的平均污染物浓度显著降低。带有架空层的建筑物墙壁上和靠近它的行人呼吸平面上的平均污染物浓度接近零。这些发现有助于缓解由高层建筑组成的街道峡谷内的交通污染，特别是在热带城市。
