Assessment of exhaled pathogenic droplet dispersion and indoor-outdoor exposure risk in urban street with naturally-ventilated buildings
Assessment of exhaled pathogenic droplet dispersion and indoor-outdoor exposure risk in urban street with naturally-ventilated buildings
复制标题
DOI：
10.1016/j.buildenv.2023.110122
复制
发表时间：
2023-02
影响因子：
7.4
通讯作者：
Jian Hang;Xia Yang;Cuiyun Ou;Zhiwen Luo;Xiaodan Fan;Xuelin Zhang;Zhonglin Gu;Xianxiang Li
中科院分区：
文献类型：
--
作者：
Jian Hang;Xia Yang;Cuiyun Ou;Zhiwen Luo;Xiaodan Fan;Xuelin Zhang;Zhonglin Gu;Xianxiang Li
室外飞沫暴露风险一般被认为比室内要小得多，但这样的室内外评估和比较仍然很少见。通过室内和室外环境的耦合，数值模拟了两个八层单面自然通风建筑的典型街道峡谷(室外，纵横比H/W=2.1)和每个房间(室内)内呼出的病原体微滴(直径d=约10μm)的通风与扩散。计算两个面对面人群之间的吸入分数(IF)和悬浮分数(SF)，以量化和比较8个楼层的所有16个房间(室内)和两个室外地点的人与人接触的风险。结果表明，与2-7层(∼4-11)相比，1层和8层房间的每小时换气率(−4.5-6.6ppm)更高，暴露风险(∼2-4ppm)更低(∼1.6ppm-5.3ppm/h−1)。虽然存在楼层间的液滴分散，但有指标者的房间比其他没有指标者的房间暴露风险高2-4个数量级。当指标患者停留在户外时，室外IF会随着位置的不同而变化，即背风角的∼为55ppm(甚至超过室内IF∼2-11ppm)，中街的∼为7ppm。因此，室外感染的风险不容忽视，尤其是背风街角的人群，那里存在着小涡流，导致局部通风不良。特别是，室外IF值取决于短距离雾滴暴露(∼1米)和主要环流通过整个街道峡谷的长途空中传播(∼50-100米)。
Outdoor droplet exposure risk is generally regarded much smaller than that indoor, but such indoor-outdoor assessment and comparison are still rare. By coupling indoor and outdoor environments, we numerically simulate the ventilation and dispersion of exhaled pathogenic droplets (e.g., diameterd= 10 μm) within typical street canyon (outdoor, aspect ratioH/W= 1) and each room (indoor) of two eight-floor single-sided naturally-ventilated buildings. Inhaled fraction (IF) and suspended fraction (SF) between two face-to-face people are calculated to quantify and compare the human-to-human exposure risk in all 16 rooms (indoor) on eight floors and those at two outdoor sites. Numerical simulations are validated well by wind tunnel experiments.Results show that, the rooms in the 1st and 8th floors attain greater air change rate per hour (∼4.5–6.6 h−1) and the lower exposure risk (IF∼2–4 ppm) than the 2nd-7th floors (air change rate per hour∼1.6–5.3 h−1,IF∼4–11 ppm). Although inter-floor droplet dispersion exists, the room with index patient attains 2–4 order greater exposure risk than the other rooms without index patient. When the index patient stays outdoor, outdoorIFwill change with locations, i.e. ∼55 ppm at leeward corner (even exceeding indoorIF∼2–11 ppm), and ∼7 ppm at middle street. Hence, the outdoor infection risk should not be ignored especially for people at leeward street corner where small vortex exists inducing local weak ventilation. Particularly, outdoorIFis decided by short-distance spraying droplet exposure (∼1 m) and long-route airborne transmissions by the main recirculation through entire street canyon (∼50–100 m).